T-Mobile said unofficially last month, that there are over 1 million iPhones on their network. So if you are a T-Mobile user (like me) and have an iPhone (like me), you can now upgrade to the iPhone 4 or future iPhone with ease. Before, if you wanted an iPhone 4, you would have to cut your current T-Mobile SIM to size. T-Mobile is offering the Micro SIM for free to customers who sign a new 2 year contract.
T-Mobile is still in limbo of being sold to AT&T, which would bring the iPhone automatically to T-Mobile customers. However, there is a lot of politicians who are against the merger, stating it would not give consumers choice and would to large of a monopoly. If however, the deal does go through, AT&T said it would take a couple years to combine the 2 companies, saying they would stay independent for a couple years after the deal finalized. With that being said, it is stil very possible we will see the iPhone 5 join the T-Mobile lineup of phones.