Supposedly the guys at The Game Reviews talked to some of the devs at the Video Game Awards conference, where they confirmed a 2009 release date. So far, that's the most substantiative release date that we have.
PS3Center is probably using thenold EGM rumor as a source, which stated that it would be GoW vs GoW this holiday season. They were right about Gears 2, so I can only hope that GoW3 will make it out that soon.