You probably heard already that Microsoft's 343 Industries is working a series of anime short-films based on the Halo universe, called Halo Legends. However, if you were under the impression that you'd be learning some profound or shocking details about Master Chief's storyline in the films, you're about to be disappointed.
With regards to what fans can expect from Legends, 343 Industries' creative director Frank O'Connor (and former Bungie big brain), confirmed during the Comic-Con 09 Halo panel, "There's a few nuggets in [Halo Legends] about Master Chief's future," however, "We don't go much further than the end of Halo 3."