Letting separate teams handle the single-player and multiplayer elements respectively of a blockbuster title isn't exactly unprecedented, and it's probably a good idea.
According to information acquired at Twitter and LinkedIn and as noted at GamesRadar , the multiplayer aspect of the hotly anticipated Assassin's Creed III will be handled by Ubisoft Annecy, the team responsible for the multiplayer component in Assassin's Creed: Brotherhood and three Splinter Cell titles; Pandora Tomorrow , Chaos Theory , and Double Agent . They also assisted with the multiplayer in Revelations .
Right now, we know next to nothing about the multiplayer in ACIII, but we could probably make a few educated guesses based on recent franchise entries. It'll be interesting to see what Ubisoft Annecy does to take advantage of the new colonial America setting, and what new modes and styles of gameplay we might see. Of course, we're fairly certain that most fans will purchase the game for what should be a memorable single-player campaign. But good multiplayer never hurts.
We'll let you know when more info for ACIII becomes available. It currently holds an October 30, 2012 launch date.