The recent outbreak of cold weather will help reduce the mosquito population in North Texas, but it won't kill all of them.
Mosquitoes become much less active as temperatures fall into the 50s. During a typical winter, mosquitoes will hibernate. Those that hibernate in areas that are susceptible to freezing temperatures will die due to the cold.
However any mosquito eggs that were laid in warmer weather are resistant to freezing temperatures. The eggs will be dormant in the cold weather, but hatch once the weather warms up.
So living and hibernating mosquitoes can be killed by below freezing temperatures, but mosquito eggs can live to see warmer weather.