Ok, really, anyone who hasn't accepted by now that the game is set during the AR, you have no hope. We've known since way before it was announced. We knew the game would have to move forward chronologically a t least a couple hundred years to a relevant point in time. We knew New York would play a major role. We knew they had to bring Desmond's heritage to the USA. Did anyone seriously think they were going to go backwards in time? Really?
Japan and Egypt are overdone for these kinds of games. I won't say that about WW2, because A) there is SO much that has never been covered in any WW2 form of media (any of you guys fought the Nazi's in Alaska yet? No?) B) The game would be very different from a traditional WW2 game in terms of story.
So I think that should be an option someday. The series, at some point, is going to have to have a revamping to keep it going anyways, and that may be a great way to do it. In my mind, it would play in some respects like AC3 will, having to be quick and stealthy in some scenarios, and others where you find yourself right in the midst of an explosive battle, sprinting across the rooftops of a town while it's being shelled with artillery fire, with soldiers trying to take you out as you make way for your target, but with modernized controls and features (along with a few oldies) Besides, it'd be cool to go to Italy one more time and see if Ezio may have a few more secrets to give in the same way Altair did in AC2.