IIRC, they have said in an interview @ E3 that there would be a demo... lemme dig it up.I would not rule out a small teaser demo, the disc isn't gold yet.
edit:
http://www.youtube.com/watch?v=4DuxCj0HGQM#t=4m
Indeed, that would be a more strategically sound plan. They have mentioned a March release, any other big PS3 titles coming around then?I don't think you need God of War to promote God of War. That is to say I think the point of bundling demos (or beta access, as has been the recent trend) in such cases is to increase exposure of lesser known franchises (or new IPs) using more established and popular IPs.
For example, bundling the GoWIII demo with a game like MAG might help sales there.