I don't see it, I'm certain GT6 is in development for the PS4. All of Sony's games are set to release on the PS3 before the PS4 comes out and unlike third parties, they don't seem to want to do cross gen titles.
I'm betting GT6 is coming Christmas 2014 on PS4, enough time not to overshadow DriveClub but still quick enough to have a big affect on hardware sales :)