• Hamilton, which historically sold out months of performances within minutes, has plenty of opening week availability and only one performance between September and June 2022 is sold out.
• London's West End theater district reopening has not gone well, with starts and stops and Sir Andrew Lloyd Webber saying, "Who knows when we will open here? 2084?"
• Some Broadway theater owners and producers say even though it is a notoriously tough industry to make a profit in, the show must go on, even if the delta variant is creating more challenges and ticket buyers will wait longer than ever before to purchase.

Investing in a Broadway show is a high-risk venture: only one out of five productions recoup their investment. But the 20% of profitable productions – such as "Hamilton" – often rake in massive revenue for their investors.

But that was before Covid.

With the New York theatre industry closed for over a year and theatregoers hesitant to return to crowded indoor spaces amidst a substantial increase in Covid cases associated with the delta variant, producers have cause for concern. Ticket sales are not booming back.

On September 14, three highly profitable mega musicals: "Hamilton," "Wicked," and "The Lion King," will be among the first Broadway musicals to open at 100% capacity. Although tickets have been on sale for months, neither "Wicked" nor "The Lion King" – the top two highest-grossing musicals in history – sold out their first week of performances. "Hamilton," which historically sold out months of performances within minutes, also has plenty of opening week availability. Between September 14, 2021, and June 5, 2022, only one performance of "Hamilton" is sold out.

"Wicked" producers declined to comment. The producers of "Hamilton" did not respond to requests for comment.

John Kenrick, an American theater historian, lyricist, and theater producer who has worked on several Broadway musical productions, including the 1994 revival of "Grease" and "Rent," says Broadway producers have significant reason to be concerned. "Every production, regardless of its size, is facing the question of life and death," he said.

Both on and off Broadway, live event venue producers attribute the sluggish ticket sales to industry volatility caused by the delta variant. Michael Rosenberg, managing director of the McCarter Theatre, a major regional theatre in Princeton, NJ. and former managing director of La Jolla Playhouse in California, said it is to be expected that theatergoers will be hesitant, but that is not a reason to stop the show.

"When shows are reopening, people are making their buying decisions much more closely to the performance date than we're used to seeing," said Rosenberg. "People are going to be a little more cautious about [buying tickets] eight weeks, nine weeks, ten weeks out."

The pandemic already forced five Broadway productions to close and postponed the opening dates of seven other productions – many of whose fates remains unknown.

Should Broadway take its shot?

While Broadway's reopening may have seemed on surer footing two months ago, the surge in Covid cases due to the highly transmissible Delta variant questions the decision to reopen in September.

"The theater-going public are voting with their dollars," Kenrick said. "If you rush this, it's going to cost you a lot more than if you take it slow and steady."

While the Broadway League announced measures on July 30 to prevent the spread of Covid – such as mask and vaccination requirements for all Broadway theatres – Kenrick remains skeptical.

In a sign of the uncertainty, the Broadway League announced it will not be distributing box office grosses for the 2021-22 season, a decision it said was based on factors including the staggered roll-out of returning and new productions, and anticipated variations in performance schedules.

London's equivalent reopening experiment doesn't instill confidence.

On July 19, London's West End attempted to reopen when capacity restrictions were lifted. Andrew Lloyd Webber's $8.1 million production of "Cinderella" canceled its opening night performance after a cast member tested positive for Covid. Lloyd Webber halted performances indefinitely on July 19, and on July 23, he announced the production would open August 18. However, in an interview with The Telegraph, Lloyd Webber stated: "who knows when we will open here? 2084?"

Andrew Lloyd Webber, through his firm, did not respond to a request for comment.

Other productions in London, including "Hairspray," "Romeo & Juliet," "Bach and Sons," and "The Prince of Egypt," canceled performances due to confirmed or suspected Covid cases. The London Coliseum, where "Hairspray" currently performs, merely "encourages" face coverings and does not require patrons to be vaccinated. London has multiple theater organizations, but none enforce Covid guidelines like the Broadway League, mostly pointing to "recent government guidance." 

Kenrick believes a successful reopening can only occur if producers wait until the pandemic is under control. Otherwise, Broadway will suffer the same fate as London: productions will close for weeks on end only to open for a few days before closing once more. The financial consequences of this strategy are potentially enormous.

"Covid does not operate on our calendar," he said. "It doesn't give a damn about our financial needs. Until everybody gets a lot more sensible about that, we're going to pay a price for it."

Matt Ross, a producer of the Broadway play "Pass Over" – which opened last week for previews to full capacity – says Broadway should not postpone re-opening. The show has a limited run of nine weeks, and the producer told CNBC it is "selling well," though it isn't selling out — but it is a new dramatic production rather than a mega-hit musical. In a theater of roughly 1,200 seats, a little over 100 seats were available for a recent performance. It is the second production to appear on Broadway since the Covid-19 pandemic.

"The mindset of, 'let's just wait for everything to blow over,' we've now learned that's wrong," said Ross. "That's not how you live with a virus, with a pandemic, with an infectious disease."

Pass Over, in fact, moved up its opening date, with Ross recently telling Playbill, "We built our schedule with more time than we would need knowing there was a real possibility we would need to delay rehearsals or previews."

While regional theater manager Rosenberg is in favor of a September reopening, he does have concerns about the volatile start again-stop again situation in London.

"[This model] can't be sustainable in the long-term. It's an enormous cost to start these shows back up again," Rosenberg said. "The start and stop again thing will be really problematic if that also happens here."

Ross even hired an epidemiologist for the production to help prevent such an occurrence. The epidemiologist helped the team design a plan to keep the audience and cast safe to minimize the risk of needing to cancel or pause performances. The production has an intense testing protocol, more than 4 times a week, a fully vaccinated company, contact tracing, backup testing options, and the epidemiologist "walks them through these situations," Ross said. "We're definitely trying to avoid that stop again, start again model."

Broadway's biggest star is tourists

A big factor in Broadway's ability to be financially successful, though, remains a major wildcard: tourists. With tourists accounting for 70% of Broadway ticket sales, show business is in trouble. According to the Office of the New York State Comptroller, tourism in New York City decreased from 66.6 million visitors in 2019 to 22.3 million visitors in 2020: a 67% reduction. The office projects 36.1 million visitors in 2021. To combat the substantial decrease in tourists, Mayor Bill de Blasio announced a $30 million promotional campaign funded by federal relief funds.

Rosenberg expressed concern about the return of Broadway's most populous audience.

"There's a large chunk of that Broadway audience that is a tourism audience," he said. "That tourist audience, I think, is going to take a little longer to come back."

That's another reason Kenrick believes Broadway should wait until the entire tourist industry and downtown Manhattan are revitalized.

"The theater industry supports over 96,000 jobs in Manhattan. The people working on specific shows add up to just a fraction of that amount," Kenrick said. "The majority are hotel workers, restaurant workers, shop people, all the people whose jobs center around the presence of theater in New York."

He believes small-scale, inexpensive, and independently produced productions will be the first to make a healthy comeback. Corporations, such as Disney, that produce large scale, multi-million-dollar musicals may be looking in other directions.

For example, Disney's most recent production, the $30 million "Frozen," grossed $155 million (compared to over $1.6 billion gross revenue for "The Lion King" and over $460 million gross revenue for "Aladdin"). While "Frozen" ran for only 851 performances, Disney's mega musical hits have been running for 22 and 6 years, respectively. While "Frozen" was based on the second highest-grossing animated film of all time, even before Covid hit it did not meet expectations.

"What was risky before is riskier now, even for Disney," Kenrick said, especially as their target audience is young kids, many of whom are currently unable to get the vaccine.

Disney Theatricals declined to comment.

The Broadway League's decision to mandate vaccinations was the right move, Rosenberg said, but he suspects it could have an impact on productions that cater to younger audiences.

"I think it could be tricky for some shows that have an audience that's younger, that's under the age of 12, since they can't be vaccinated at this point," he said.

Kenrick says Disney will need to be thoughtful about maintaining the vitality of Its current Broadway properties. If Disney does open a new production, he believes the company would be better off with a revival – productions with proven track records and high profitability.

"Bringing back "Mary Poppins" or "Beauty and the Beast" will prove to [Disney] whether or not Broadway is still worth new investment in new productions," Kenrick said.

Taking live theater onto film and streaming

During the pandemic, Disney debuted the filmed version of "Hamilton" streaming on Disney+, though the theatre industry has largely shied away from filming and distributing productions for profit (some productions have been filmed for educational use, but countless productions have not been recorded).

The online audience is "a huge audience theater has ignored for far too long," Kenrick said. "It would be utterly foolish if people did not take advantage of that." He added, "You can let people continue to do that illegally, and profit from it illegally. Or you can make it part of the package."

Streaming is a part of the theater industry's future, according to Ross. "There's money to be made," he said, and offering recorded productions will strengthen the industry. "We want to share this story with as many people as possible. We need to acknowledge that even when we go on tour, there are still people through either geographic or financial barriers who are not able to see these shows."

On its latest earnings call Thursday afternoon, after a quarter in which Disney's theme parks bounced back and led to financial outperformance compared to Wall Street expectations, there was discussion of the future of theatrical releases of films, but no discussion of the live Theatricals business.

Filmed productions are a relatively untapped market, and so it is difficult to gauge whether they become part of a new normal in the theatre industry. But the current situation for live theater is a pivotal moment, and producers may be too eager to reopen and go back to the way things were before Covid.

"If 'Lion King' is having that kind of trouble selling tickets right now, who isn't?" said Kenrick. "So that's got to have everybody wondering, are we going too fast too soon?"

—By Ryan Waterman Aldana, special to CNBC.com. Waterman Aldana is a summer 2021 talent development intern at CNBC.