CVG reports that the Xbox 360 patch was sent out to prepare the game for upcoming DLC and "some major updates." But server issues caused a multiplayer glitch, which has since been fixed. Downloading the current patch should leave you error-free.
BOOM video 7684
And not a moment too soon. Today the free Animus 2.0 update hit Xbox Live and PlayStation Network, adding a Chest Capture mode, Templar Score feature and a new Pienza map. So far Ubisoft hasn't discussed future DLC plans, but the company has garnered some goodwill among gamers by offering two moderately sized multiplayer expansions free of charge.