Graphics aren't everything
GT6 looks very much improved even though not all has been announced- at least 200 brand new premium cars(well, some are from 1957) and has an improved physics model, adaptive tessellation(cutting down the processing power needed) and everyone is expecting some kind of livery editor to be officially announced at the Tokyo Game Show next month, along with several updated features.
If you haven't bought the game yet, get it. Get the XL edition(Comes with many DLC cars+tracks) and you can get it new for around $15. Gran Turismo 6 will come out in early December and trust me, that will be all it's cracked up to be.