Don't expect this as a Gran Turismo coming out anytime soon. Gran Turismo 5 took a long time to release upon its announcement so just realize that fact. Yamauchi made some comments on Gran Turismo during the China Joy game event in Beijing. Although details were very vague he did have this to say on the potential title(s). Yamauchi is indeed working on Gran Turismo 6 and has been after Gran Turismo 5. He expects to progress the series with the newest and latest technology which means even longer development times for those who want a new entry as soon as possible. Yamauchi also commented on a Vita version saying this...
l4d LittleBigPlanet Karting Beta Code Contest Giveaway: M869-MAN2-C8NE
If we were to make it, we'd like to make use of the ability to play anywhere and the ability to use 3G at any time.
Thank you Andriasang for the info.