Earlier quoted context omitted.
I would peg it at "Highly unlikely" since most of the world uses GSM and CDMA carriers are a pain in the ass to support iirc.
Sprint, Verizon, and US Cellular refuse to unlock their phones, and even if you convince someone to do it, they won't activate a phone that wasn't originally bought on their network. So I doubt that's going to happen.
I actually get a pretty decent price from them for running an iPhone 4S [my employer offers a discount for sprint services], but I'd like to move it to T-Mobile as they would offer a much faster network. Sprint's 3G is terrible here in SE Wisconsin.
Of course: Sprint won't unlock my iPhone, even though it's the exact same hardware that Apple/T-Mobile would sell me. Selling my 4S, of course, means losing my ability to jailbreak.
(I don't plan to move to a newer iPhone, as I hate the form-factor of the iPhone 5... but I also don't want to spend another $600+ on an Android or Windows flagship phone.)