Some of ours won't.
I've heard some conflicting reports whether we would be impacted or not. I think just about all of our multisites are okay. The new gear is compatible. Some of our old gear, however, isn't compatible. D'OH!
Here's the deal. Evidently the FCC sold public domain frequencies, and several of our Shure Wireless Handheld/Beltpack Microphones run on the frequencies that the FCC sold to AT&T and Verizon.
Officially, the transaction doesn't complete until February 2009... but even at that point, it could be a number of months/years before AT&T and Verizon publically release devices that would use that frequency...
So, essentially, our wireless mics are on borrowed time.
Does your microphone run on "borrowed" frequencies? If you're not sure, get the model number of your wireless receiver and contact the manufacturer. I've found them to be quite helpful!