For T-Mobile, not sure anything good is coming out soon. There is a rumor the HTC One X could come to T-Mobile, but right now it's only announced for AT&T. So it could be a long time before T-Mobile gets it.
HTC One S is coming to T-Mobile. If you like the 4.3 inch size and don't mind the lesser resolution, then it looks like a nice phone.
Rumor has it the LG Optimus 4X could arrive on T-Mobile as the G4X. I like this phone a lot, because it has a larger battery (which I hope is removable) and it has micro SD. The camera isn't as nice as the HTC One X (or One S), if that's important to you. But zero word on when or if it really is coming to T-Mobile.
Carriers are so slow, even with phones being announced this spring like the One X and LG Optimus 4X, god only knows when the carriers will have them available.
For T-Mobile, the Galaxy S 2 looks like it's still your only good option. Or even better the Galaxy Nexus GSM if you want to pay full price and maybe try out T-Mobile's Monthly4G prepaid plan.