The next iteration has cameras, a new screen, a new SD slot and, probably most important, a new chip set.
Qualcomm is moving up in the world and into Apple's skinnier iPad. They're replacing Infineon chips, as announced later last year. The dual chipset is most likely designed so the new iPad can run on both AT&T and Verizon at launch.
Launch? At least Engadget has the rumor set at an April launch -- not the somewhat infuriating late-January launch that was previously rumored.