Slipped at the end of its outlook for the 2010-2011 fiscal year that starts in April, Ubisoft announced a new Assassin's Creed game promising online multiplayer.
Ubisoft didn't state the game would be Assassin's Creed III proper, instead offering up "a new episode of Assassin's Creed, which will be the first in the series to have an online multiplayer mode."
New episode and sequel mean different things and when you consider that this game is supposed to be out within the next year, a full sequel seems unlikely.
We're probably talking about an offshoot games that branches from the previous two titles or downloadable content, though the former sounds most likely. Naturally, we'll keep you posted.