Although video game films often have a hard time becoming a success at the box office [with the exception being Lara Croft], Fox is hoping that Assassin's Creed can buck the trend. The studio picked up the rights to the popular Ubisoft game a couple of years ago, and set Michael Fassbender to star as the lead. Now, the studio has announced that they have picked a prime release date for the film on May 22nd, 2015.
This means that Assassin's Creed will release on Memorial Weekend in 2015, possibly competing with Star Wars: Episode VII if Disney decides to keep their traditional summer weekend [where previous Star Wars films have released].
Michael Lesslie is currently writing the screenplay for Assassin's Creed, and expectations from the studio are very high. There is currently no director attached, but the movie will likely go into pre-production pretty soon. For a film like this, there will be some extensive post-production work and they'll need to do test screenings to make sure that they don't have another video game flop on their hands.
Also, Michael Fassbender has a pretty full slate of movies coming up in addition to Assassin's Creed. While I'm sure the studio's already keeping that in mind, Fassbender is currently shooting X-Men: Days of Future Past and has Prometheus 2 and Genius in development.