That'd be amazing. I've seldom felt as immersed in a game – I loved the story and the atmosphere. The story of Marathon: Infinity was so mind-bogglingly complex that fans were still discussing and trying to figure it out ten years later. I don't believe there'll be another Marathon game though. However, the fans have done an amazing work keeping the story and universe alive through scenarios (mods/conversions, whatever you call them) such as Rubicon and Eternal.
Oh, and it's a shame Double Aught never managed to release it's game Duality.
The F-15 Eagle: If it's up, we'll shoot it down. If it's down, we'll blow it up. -- A McDonnel-Douglas ad from a few years ago