The following comes from a Kotaku interview with Ubisoft CEO Yves Guillemot.

"We are making sure the teams who are creating the different iterations have enough time—two years, three years, so that they can take risk and they can change the concept enough so that it can be appealing and fresh. Really, what we see is that we can have the capacity to regularly come with innovation. That is, for me, the formula: if you can really change the game on a regular basis and bring in innovation your fans want a product very regularly. Our job is to make sure the teams have enough power, enough energy and enough time to take the necessary steps to create a high quality game."

Guillemot confirmed that Ubisoft currently has 3 Assassin's Creed games in the works.