Gears of War 3 was originally planned for an April release, but after an announced delay, the title was pushed back to a vague Fall-ish timetable. The franchise is an important one for Microsoft, who has not been receiving quite the same level of exposure for their exclusive titles that the PS3 has, so expect a lot of hype around this title as the release date approaches.
The third game in the series promises to be the end of this particular trilogy, although the series may (and probably will) continue beyond, but with a new story arc. The game will begin eighteen months after the conclusion of the previous title, with the survivors living on an island aboard a converted aircraft carrier. The imulsion continues to spread, and vast numbers of Locust have become the Lambent, a new threat to both the Gears and the surviving members of the Locust race.
The game will also feature a hefty online side, as well as co-op. It will be released as an Xbox 360 exclusive on September 20.