On Friday, Microsoft let slip that the next chapter in the Gears of War series from Epic Games would be released in April 2011.

The announcement wasn’t made via an expensive commercial or billboard or skywriting, but on the Xbox 360 dashboard.

Things were supposed to go much differently: Gears of War designer Cliff Bleszinski was scheduled to appear on Late Night With Jimmy Fallon Thursday, where he was expected to announce the game. But his slot on the show was rescheduled to Monday.

And though rumors swirled that Canadian teen idol Justin Bieber bumped Bleszinski, the game designer insisted via Twitter that the rescheduling was his idea: “As much as I’d like to start a fight with @justinbieber the truth of the matter is that we wanted to take a couple more days to polish,” he said.

Unfortunately, nobody told the person in charge of Xbox 360 dashboard updates about the postponement of the game’s big reveal. Gamers who turned on their Xbox 360 this morning saw an ad touting the announcement that was never officially made.

Gears of War, an Xbox 360 and PC game series about solders fending off an alien invasion, debuted in 2006. Hollywood has its eyes on the third-person shooter, but the Los Angeles Times reports that chances of a big-screen adaptation are becoming more and more unlikely.