Halo: Combat Evolved Anniversary - Remake of the original ass-kicking Halo that spawned the equally as ass-kicking franchise. It will feature revamped graphics and sound, connection to Xbox LIVE, and the Halo: Reach engine for its multiplayer. It will be released on November 15, 2011, the ten-year anniversary of the original game's release.
Halo 4 - Not much is known at this point, except that it will continue the story of the Master Chief and Cortana and leave off immediately after the ending of Halo 3. It's interim release date is "Holiday 2012," as no final realease date has been announced by 343 Industries.