I think the only safe answer at this point is we can assume that their will be a GSM version of the device shown by Motorola.  I'm guessing that the Brazilian leak happened sooner than expected.  You will probably see some adoption of the device stateside, but I don't think anyone can be sure for now.  I think most GSM devices can be unlocked to run on AT&T or TMo, but unless adopted by the specific carrier you might be missing some carrier specific features (i.e. WiFi calling, etc..).  Again, I'm sure more information will come out soon enough, but I really think this information got to folks before it was supposed .