Due to the success of Assassin's Creed 2, Ubisoft has stated that another Assassin's Creed is on it's way before April 2011. Assassin's Creed 2 has sold over 8 million copies since it was launched on the Xbox 360 and PS3 in November of 2009. The original Assassin's Creed sold that many copies 18 months after it was released.
Details on the new Assassin's Creed (3?) have not yet been released, but Guillemot has stated that "This time, [Ezio] will strike directly against the templar's order in Rome."
With no details on the new Assassin's Creed, one begins to wonder if they will be able to release it at the end of this year.