Vision Gran Turismo is probably an working - or even final title of the GT game that will follow the launch of PS3. Guess form the info we have witnessed so far, that making a "Vision" was a main reason for delaying a GT4 release.
I'm pretty conviced that PD had their work on VGT for a long time now, making parallel development of both GT4 and VGT in lat years. The vast number of astonishing footages shown in LA only few hours ago shows us that Sony had a great secret work undergone with the console for a long time now.
VGT should be "just" GT4 on super-stereoids, but for me - it is more then enough for a start. I agree that next "full'n'big" GT game will come out no sooner then 2007.
Notice the VGT should be the title needed for establishing the GT Online Leagues for the first time, and that all the work has been done in that direction.
My dime goes to AI field in multiplayer (2P and LAN) races.