Personally, I've never cared all that much about the VGT cars (I do realize that some people like them, just saying for me personally or whatever) but one thing I would DEFINITELY like to see more of would the F1 cars. In GT5 they had not just the Formula Gran Turismo and the Lotus, but additionally they had two recent/current real life F1 cars from Ferrari (the F2007 and F'10 I think it was). And I think they might've been "premium"-style, too, although I can't remember for sure.
But yea, it would be really cool to get at least a couple of current or within-past-5-years-or-so real life F1 cars. maybe the Red Bull F1 car from when it was in its prime 3 or 4 years ago, or one of the Mercedes F1 cars or Ferrari F1 cars from the past few years. But heck, I'd even be thrilled with even one of the lower-level F1 cars from like Sauber or Caterham or what have you, if licensing costs is their reason for not bothering, just SOMETHING, as long as it is from within the past few years and a real life non-fictional model (unlike the Formula Gran Turismo which is a fictional car (not that there's anything wrong with that, but, just saying it would be nice to have 1 real one from more recently than the 1980's). And done in premium visual representation, preferably.
It just seems like a bad idea not to have at least 1 or 2 like they had in GT5, when considering how many Gran Turismo players are bigtime F1 fans, and enjoy driving the F1 cars on the 6 or 7 real world tracks in the game that are part of the current F1 racing tracks (i.e. Silverstone, Spa Francorchamps, Red Bull Racetrack, Monaco (aka Cote d'Azur), Monza, Suzuka (and some recent/alternating/previous etc ones like Nurburging-GP track, and Fuji and whatnot).