2012: AC3: American Revolution
2013: AC3-1: Washington, D.C.
2014: AC4 for next gen: current/near-future city setting w/ cliffhanger & guns (final Templer vs Assassins fight)
2015: AC4-1: Real conclusion of the series
(+ DLC episodes. Also more games depending on release of next gen consoles and success)
After the first two games I hoped they would go into all kinds of interesting eras (as in, not that often featured in media). Like B.C.-Egypt, feudal Japan, China during unification, Russia during Tsarist autocracy etc. etc. etc. I would buy those just to see a recreation of the cities/the "daily life" of those people.
Brotherhood already burned me out big time on the series. I'm happy AC3 will finally continue to a different time etc., though this setting is not my first choice to say the least.
btw, I wonder if they will change the gameplay for AC3, from my impression the US cities during that time were quite open&ordered. Not sure if that works with the gameplay style of the previous games. Maybe they will focus more on the rural areas.