It really has nothing to do with how big a device this is for Sprint. Their world phones tend to be more business oriented, not multimedia centric. The TP2 is a winblow phones aimed at business users, just like their BB Tour which is also a world phone.
You won't see a GSM version of the Evo either since this phone is made exclusively for Sprint due to the 4G. IF a variant will be made for GSM it will be called something else entirely and won't even look the same.