i made a thread about this also but ill put it in here too. :)
What this Japanese article says.
http://www.imagebam.com/image/10738145810998
Its in the bottom left corner about GT5. Heading reads "GT5 on PS3 Playable"
Article says that GT5 will be playable at Gamescom and next up will be at Tokyo Game Show.
Whoo hoo!! cant wait for the vids.