I honestly doubt that Android will be a T-Mobile or even a GSM exclusive- isn't Sprint a member of the Open Handset Alliance?
HTC's specialty is GSM phones, and they usually release GSM versions of their phones long before CDMA equivalents. (And usually Europe/Asia long before the USA, if they reach our shores at all) Plus, I believe T-Mobile International (the 6th largest world cellular carrier) has been pushing this heavily.
