Feudal Japan?
Vikings?
Genghis Khan + Mongolia?

I like this one :) that would be awesome.

It's going to be Rome (probably during the fall of the Empire) considering that Origins and Odyssey are chronologically linked. The logical next step.

I think Ubisoft should revamp the fighting system. It should become slower and more risky and complex, like Dark Souls or Monster Hunter. That would be a great way to refresh the IP.

Roman Empire during the time of Ceasar would be nice. To travel rome as its greatest time!
And why not Berlin? Maybe between WW1 and WW2? Lots of political things happened there.

Dystopian future setting or the Punic Wars with Rome and Carthage (you march with Hannibal and his war elephants).

Also, there were three Punic wars. Perfect setup for a trilogy.

China or Japan. Something about Rome would be great too, and it sounds like it could be next. I'd also like the series to go even further back in time because we rarely get to explore even older eras. I was actually somewhat disappointed at Origins being set in such 'recent' times as Egypt's prime was already way gone. Genghis Khan would obviously be another great theme. Revisiting the crusades might not be bad either, either in the form of a remake or an entirely new game.

Futuristic outer-space.

In all seriousness, I would actually like to see it tackle some of the larger events in history like the world wars, I don't see why a game needs to be fixated on one part of history in one geographical location.

HD remasters!

Norway 1814