It's here. The DOOM 3: Resurrection of Evil expansion pack has just been announced for the Xbox. It will add for your killing pleasure six new demons, and will support eight-player multi-play instead of four. New weapons, including a double-barrelled shotgun and something that's very much like a gravity gun, will make you that much more efficient at eliminating the demonic threat. Also, you'll be able to possess some sweet demon powers after defeating key bosses.
News source: 1UP.com