It seems like the next game in Assassin's Creed franchise will be reveal on February 27 (next Wednesday). Right now Ubisoft is sending mysterious invitations to an event related to Assassin's Creed series.
A tweet from MCV reads, "We've been invited to a mysterious Assassin's Creed event on Feb 27th. Anyone else going? Any idea what's planned?"
Ubisoft CEO Yves Guillemot has already confirmed that details regarding next Assassin's Creed game in 2013 will be revealed very soon.
So far the only thing we know about new Assassin's Creed game is that it will feature new hero and time setting, and is currently in development by an all new team.