The leading role will be going to Michael Fassbender who also played Magneto in X-Men: First Class as well as a leading role in Prometheus.
Ubisoft has said though that this lead character may not actually be Desmond as most people assumed. "Fassbender will play the lead role, but it's too soon to say exactly which character that will be," a Ubisoft representative told Joystiq.
Interestingly, Fassbender will also be lending his apparently deep pockets to the project as a producer. Ubisoft has so far insisted they retain control over who directs and writes the film.
With a bit of respected Hollywood talent on board, the AC film is gathering a bit of momentum. We're looking forward to seeing who Ubisoft taps to write and direct the project. We're also eagerly awaiting an official announcement that the film will not involve Jake (A.K.A. Chesty Shirtless) Gyllenhaal in any way.