Rather than read through all this, because I want to get back to my snowblowers, I think the reason we have such high expectations is because team Polyphony are such magicians in certain areas that we expect to be dazzled in all. Like damage. They have a handicap in that while other racing devs have been working on damage modeling their whole careers, Kaz has decided it wasn't what he wanted in Gran Turismo. There was one basic mechanical damage build in GT2, but then they dropped it entirely. They tried to give us something in GT5 because of a massive outcry from fans, but it looked weird with car bodies deforming like putty, much like in Live For Speed, so it was cut way back. They don't have years of experience in this, refining damage builds over the course of a series like other devs, so they have a lot of catching up to do. This is one area I think they could stand to outsource work, especially with a company gaining experience in materials modeling such as with Digital Molecular Modeling.
On the car modeling thing, space isn't an issue, it's time. When they started work on GT5, it took about six man-months to make a basic car. While it's likely they have more advanced tools to help them with this, such as tesselation tools to quickly smooth over tricky surfaces with extra polygons, these models can't build themselves and it probably still takes a darn long time. Tracks take up to four times as long or more.
And the other areas people grouse over, such as bot A.I., sound, the Movie Maker they want, all these things take resources and PS3 only has so much to go around. The Movie Maker couldn't work in GT5 because there wasn't enough system ram, and that's not changing.
GT6 is looking like a miracle game to me, because I was sure the team would have to cut back resources all over the place, beginning with image resolution, in order for GT6 to be better on PS3. Instead, the engineers went back and reworked all the code they wrote for the GT5 engine and made it tighter, more streamlined and adapted to refactoring, or adjusting itself as the game plays over time. There are even PS4 tricks like shorter loading times and on the fly tesselation, or smoothing algorithms. It seems that they improved everything without sacrificing anything, except damage, which I know is a sore point for many people.
But overall, it sounds like GT6 is going to be a dream Gran Turismo, and I can hardly wait to watch as Kaz lays down feature after feature in the upcoming game conventions. E3 is just a few weeks off...