After the recent leak of some Assassin's Creed III character artwork, which you can see here, Ubisoft decided to just release the games Official Boxart.
So it's now been confirmed that the game is to be set in the American Revolution, where Desmond will tie in to all this is still unknown.
You can also see Gameinformers April magazine cover here
Assassin's Creed III is due to release October 30th, 2012.
Thanks to Ps360 for the images