Sprint could be getting an "exclusive" on iP5 because they're the only carrier with 4G tech (WiMAX) that Apple is prepared to include right now. The other carriers would get the iP5 when LTE chipsets are mature enough for Apple's use.
Completely speculating here.
Apple wants to make one model, they like simple product lines. It would be retarded to design the iPhone 5 as a WiMax device. No one is using that standard. The iPhone 5 needs to launch on all carriers globally at once, it HAS to do this. Apple's exclusivity to AT&T opened the door for Android they aren't going to hold the door open again for them to support a useless standard that no one else is using. The next iPhone will be GSM & CDMA in one phone, or LTE. You can put money on it.
There is just no way this story is true. They got to many partners lined up release an iPhone that would be limited to one, second rate, American carrier. They are playing the game global.