According to a report in Joystiq, the original Halo - Combat Evolved is to get rolled out again with new artwork ('art assets' as per industry jargon) and controls.
The report states that the "remake of Halo: Combat Evolved
will indeed launch this holiday season for Xbox 360 with a full visual overhaul. Sources explain that the re-release is not Bungie's 2001 Xbox game simply running at a higher resolution -- it's being remade with new art assets. While Halo's audio will likely remain unaltered, the controls will allow for more recent Halo configurations."
Game's due on November 15, 2011 - guess what that date means? More here.