Well after reading various sites, there is a storm of evidence to suggest that GT5 will be at GC. Not only that but that it will be playable along with GTPSP. So I am starting this thread with both games in mind (just in case one does not show). If there is a storm of news we should probably keep it in one place instead of flooding the news, media and comments thread along with the board in general (hope this is ok). So I will get the ball rolling. I will update this thread to the best of my ability but you if you see something that post it.
GTPlanet says GT5 GC appearance is likely:
Famitsu says GT5 and GTPSP will be at GC09 and they both will be playable:
Look at around 1:20 in this youtube video, GT5 booths... which would mean GT5 will be playable at GC: