I have heard rumors since the game came out and about a year ago it was made official. They are making a Gears of War movie, due by Summer 2009.
I believe it's still rumored that Bruce Willis is to play the lead role as Fenix (I think they should find someone better). The movie is supposed to be as accurate as possible (Unlike Silent Hill & Resident Evil).
I'm not sure if they have started the making, but it seems likely, as this movie will require much special effects. I'll post here if I get my hands on anymore news.
(March 20, 2007) New Line Cinema acquired the film rights to Epic Games. Stuart Beattie, who wrote the script to Pirates of the Carribean, has been asked to write the Gears of War script. Temple Hill is set to produce the movie.
Date of Release: Summer 2010
Director: Len Weisman
Producer: Temple Hill
Writer: Stuart Beattie
Art Director: Jerry O'Flaherty
All info from: gearsofwar.moviechronicles.com