This rumor has been on and off for awhile. It reminds of the rumors that were all over the place back when the Moto RAZR was the "must have" cell phone.
If Apple
does want do something outside of legacy partner AT&T, it would be with one of the two "CDMA" carriers in the U.S. -- those two carriers being Verizon Wireless and Sprint (Sorry T-Mobile subscribers -- I can't see Apple ever setting-up camp with a rival GSM carrier).
Of course, this will require a completely redesigned phone, since AT&T-requistioned phones are not compatible with either VZW or Sprint's networks.
As for which of the two carriers would get the next-gen iPhone, I would have to say Verizon, because of their monstorous number of subscibers, plus, they are in the process of rolling-out a 4G network, which would be very complimentary to the iPhone.
Post #1000 for me!