Right now, it's unclear if Bungie will continue making Halo games after next year's Halo: Reach. However, Microsoft has no plans to abandon its bread-and-butter Xbox 360 franchise until well into the next decade--at the earliest.
After telling USA Today that Halo 3: ODST had sold 2.5 million units in two weeks, Frank O'Connor, creative director for Microsoft Halo label 343 Industries, laid out his company's vision for the franchise. "We do have a plan that goes out at least six years," O'Connor told the daily.
Specifically, O'Connor pointed to [SPOILER WARNING] Halo 3's legendary-setting ending as a jumping-off point for the main storyline's continuation. "I think that [the Master Chief's] fate, Cortana's fate and the identity of that giant, dark planet at the ending are probably big mysteries that would be irritating if they were just cliffhangers," he said.
With the next Halo game, Halo: Reach, confirmed as being a prequel (as was expected), the future of the Master Chief storyline will continue in a variety of properties, including games, books, comics, and animated efforts like the forthcoming Halo Legends, due out next year. "Eventually, it will become very apparent that there is a plan for the way the canon all ties together and the way the comic books and the novels all tie together," said O'Connor.
The next Halo book, the short-story compilation Halo: Evolutions, will be published this November by Tor Books. The imprint has also commissioned a trilogy of new Halo novels from Greg Bear, author of such acclaimed books as Blood Music and The Forge of God, to begin next year.
As far as comics go, Marvel is currently halfway through its limited series Halo: Helljumper, which profiles the same sort of Orbital Drop Shock Troopers featured in Halo 3: ODST. The new series Halo: Blood Line (pictured bottom), which chronicles a group of Master Chief's SPARTAN comrades, will begin on December 23.