Ubisoft have begun teasing about Assassin's Creed 2, shooting through a link to a teaser site with a very short, but interesting video that seems centered around the inclusion of Leonardo da Vinci as a key factor in, at the very least, the tools of the Assassin's Creed trade.
While not a lot is shown, it's interesting the video hovers
around the flying apparatus sketch, possibly indicating further to the rumour Altair will be swimming in the next game (as revealed by AusGamers at last year's TGS), he may well be able to fly/glide in the sequel.
Obviously this is just speculation, so head over to the teaser site
and have a look for yourself.