A new trailer is up, focusing on Assassin's Creed: Brotherhood's story. A lot of new things can be concluded about it. Ezio is the leader of the Assassin Order (yeah-eah, Jasca!) and Cesare Borgia is killed by Ezio in Spain in 1507.
Check the trailer out here: http://www.youtube.com/watch?v=Yfw4WbnVqjg&feature=player_embedded# .