In very exciting news today, it has been annouced that Prometheus and X-Men: First Class actor Michael Fassbender will be not only producing but starring as Desmond Miles/Altair in an adaptation of Ubisoft's Assassin's Creed series.
While details are scant at the moment, this would corroberate previous stories describing how Ubisoft wants to do Assassin's Creed 'properly.' The company is waiting for a writer and a director to be attached before it even begins to think about production, meaning that they are clearly very concerned about how their most valuable franchise is handled on the big screen. Considering the outright failure of Disney's Prince of Persia, this shouldn't come as much of a surprise.
So as it is, this project is still very much in development. But Fassbender's attachment is a huge step forward, considering how much clout the actor currently wields in Hollywood.