You mean, like he wouldn't stand for a carrier that wasn't ready to deploy MMS? Or tethering? Oh, wait, AT&T took forever to implement both of those functions. How selectively we forget. Simultaneous voice/data is far from a critical function. If you need it desperately and Verizon doesn't announce it on Tuesday, then you can add another positive to AT&T's column (and expect that iPhone ad to rear back up again if Apple will allow it).
The most interesting thing left to learn is whether AT&T and Verizon will get new phones on the same schedule, or will iPhone 5 be delayed on Verizon. Sadly, I doubt Verizon will reveal those details on Tuesday.