Assassin's Creed: Revelations
http://www.facebook.com/assassinscreed?sk=app_150031305061905
The actual reveal will come in the new Game Informer, so we should know more in about a week.
That almost looks like an older Ezio on the cover, with Altair...maybe it's connected to Lost Legacy?
(and I didn't use the AC3 thread because this isn't necessarily AC3 😛)
Edit: http://www.pcgamer.com/2011/05/05/assassins-creed-revelations-revealed-launches-on-pc-in-november/
So it is Ezio, it's not AC3, and Altair is playable at a point in it, apparently.
Sweeeeeet.