I have a 925 on T-Mobile and I'm living in the US. The 640 XL has interested me but T-Mobile is only going to offer the normal version(or from what I know). So I'm wondering if I should buy an unlocked 640 XL(if I can) or wait for T-Mobile to perhaps get a Windows 10 phone. I have to stay with T-Mobile because I'm on a family plan.