If you are willing to buy the international version, it appears there is no need to way for a specific ATT version. The int'l version seems to have both T-Mo and AT&T HSPA bands.
So if it comes out internationally and the AT&T version is rumored to be months and months away, you don't necessarily have to wait...
Dang, I sure as heck would've bought an international GS2 last May had I known that the AT&T version wouldn't surface til October and would be nearly identical.