I'm sorry, but I have to post this.
I'm finding it rather sad on how people are already complaining about a game that hasn't even been released, let alone has an even confirmed release date (The only confirmed release is a Demo, due for July).
First of all, Gran Turismo 6 upon it's announcement, already seemed like a surefire cash in to be on PS3 and not the upcoming PS4. Why? Simple, PD had been developing GT6 shortly after GT5 was released THREE YEARS AGO. This was well before the PS4 was even in a proper development, and no known dev kit for the PS4 properly existed back then. Not to mention, PD has had a tradition of having 2 Gran Turismos per Playstation (Gran Tuismo 1 and 2 on Playstation, Gran Turismo 3 and 4 on Playstation 2, and Gran Turismo 5 and now 6 on Playstation 3). Whilst I'm sure many of us (myself included) Would prefer GT6 on the PS3, it makes more sense to place it on the PS3 as a way to give the console a final swan-song before moving to the PS4 full time.
Second, it's rather quite impossible with the PS3's limited, outdated hardware to properly obtain 1200 Premium Cars all on one disc for the cars. Whilst I believe they could've done a GT2 where they seperated both the Arcade and Gran Turismo modes away from each other, it still shows that the PS3 is at a time where it's aging hardware is now starting to show, and though it means we won't see all Premium Cars, to see 200 new additions to the roster plus an improved Standard Model lineup (in terms of Graphics) is a nice addition to my opinion.
3rd, I can't go one day without seeing someone complaining about the sound. I don't know a single game that gets sound proper. Sure they can get close, but I've never played a racing game that properly gets the engine note of a car completely 100% accurate. The people who are already complaining about the sound, keep in mind that the only gameplay videos that are around right now are of fans who used external sources to record footage, thus distorting the sound? Not to mention, the game's currently not in a final release state, so there could be some changes along the way. For example, Gran Turismo 2's sounds were heavily revamped in the final release compared to earlier demo builds.
I've grown up and the series and will still continue to try out each iteration since I'm always intrigued to see what they do with each release. Gran Turismo 5 had many disappointing things about it, so I'm curious to see what they improve with GT6.