During
Ubisoft's third-quarter earnings call, Yves Guillemot, Ubisoft CEO, confirmed that the next chapter in the Assassin's Creed series will be coming in Ubisoft's 2014 fiscal year (which ends on March 31st, 2014). The game will feature a new hero in a new time period.
According to this
reddit discussion, the new Assassin's Creed title would be named
Assassin's Creed IV: Black Flags.