http://news.teamxbox.com/xbox/11490/No-Gears-of-War-Demo-Before-Emergence-Day/
"I don't see any way we could do a demo before the game comes out. We've said that before." explained Rein.
"Demos take a long time to create and polish and we can't afford to get derailled like that if we want to have the game in stores by Thanksgiving. Given a choice of the game this year or a demo this year and the game next year I'm sure every one of you would rather have the game this year because you're already planning to buy it. No idea if we'll do a demo or not after the game ships."