GSM would allow it to be used in markets without EVDO, although Amazon would need to figure out some kind of roaming agreement, flatrate data pricing, etc.
I use my Kindles (K1 and DX, I've seen other people with K2...I'll probably buy one myself for completeness) here in Afghanistan, and am probably going to set up a semi-pirate 1xRTT network, as USB gets old fast. The K1 only does EVDO (for which BTS gear is expensive), but the K2/DX do 1xRTT, so you can hack firmware on some of the consumer femtocells to remove GPS checks or spoof GPS.