Gamespot reports Polyphony Digital's Kazunori Yamauchi as hinting at a possible release of GT6 on PS4 at a later point. Or perhaps he is just referring to the next Gran Turismo following GT6...
"We have a PS4 version in mind for the future."
"But for this holiday season we thought that it would be best for users to release the PS3 version. I thought the best scenario would be for the game to come out, and we're planning to have new content, and DLC every few months."
The demo for Gran Turismo 6 on PS3 is due this July.