Speaking with Top Gear, Kazunori Yamauchi said this about the prospects of a Gran Turismo on PS4:

“We don’t want to take too long on Gran Turismo 7. Best-case scenario? Next year. In Gran Turismo 6 we really had to tune the software 100 per cent to maximize the PS3′s architecture, but of course the PS4′s hardware is much better, so I think the overall quality of the game across the board will be boosted when you come to play it.”

Gran Turismo 6 for PS3 on the other hand is due out on December 5th.