According to industry sources the newly formed Microsoft internal studio 343 Industries are working on a remake of Halo: Combat Evolved. They report that the updated game could run on the Halo: Reach engine and arrive ahead of a full Halo 3 sequel in late 2012. If there is any truth in the rumours circulating then the remade Halo: Combat Evolved could possibly release on the original games 10th anniversary, which falls on November, 2011.
The full story is detailed in Gamesmaster 233 which you can buy here.