At the end of this year, T-Mobile could start selling the iPhone...3GS

According to rumors, T-Mobile could start competing against AT&T's monopoly at the end of the year. However, it won't be a full competition as they will only be able to sell the iPhone 3GS, and not the iPhone 4.
This information, should it be true, would bring more questions than real answers. However, it is possible that the exclusivity contract between Apple and AT&T is only about the lasts generation of the iPhone and that T-Mobile found that selling the iPhone 3GS was the only way to compete a little bit with the largest carrier in the US. Apple might have even encouraged this, as they try to end the exclusivity contracts they have with carriers all over the world.