This rumor might actually be more believable than the rumors that the iPhone was going to Verizon. One main reason being that T-Mobile’s network is already a GSM network and Verizon’s wasn’t so the iPhone would not have to change drastically to connect to their network. A reason that the iPhone was not logical on Verizon’s network is because the phone design would have to change to support a CDMA network while GSM is already an international standard. According to CultofMac their source says that the iPhone coming to T-Moblie has an 80% chance to happen in Q3.
Moving to T-Mobile is a good move for Apple, it will give users in the US another choice besides AT&T and may reduce the strain on AT&T’s network. Also the fact that Apple’s exclusive contract with AT&T ends this year make this rumor possible.
Update: Status update on twitter may confirm something big to happen at T-Moble soon:
I was at the T-Mob store checking out the new Samsung Droid phone and dude told me not to upgrade til the fall. #iPhone #T-Mobile @techbitts