Sabretooth

I think they would have to go back in time, as without some extreme changes to their current engine and style of play, the Modern era would be too difficult to represent (planes, formations and tactics would be difficult to do on such a scale).

The 20th century would definately be complex, if only due to the massive changes that took place - we went from using Cavalry to Helicopter gunships in only 80-100 years!

The Big three eras have already been covered (Classical, Medieval, and now Early Modern), and of course the Shogun era of Japan, so I can't see where they would go - there's a thousand possibilities, and only Creative Assembly have any idea. But, whatever they do, it'll be certain of success.

But, they could always venture to the future - but that would be a departure from their previous games.

Besides, we've got a good two to three years of Conquering/Defending India to look forward to yet!