GT6 will be better, hopefully, if next time they forget about 3D and adjusting their in-game resources to the minor common denominator. When you want 60FPS, running at least 12 beastly-modeled cars with simulation-like physics at 1080p resolution, then you're gonna have to sacrifice something, and if you put on top of it that the whole game has to run all those assets in equal terms of quality but also in 3D (minus the resolution), you're gonna have to take even bigger cuts on what your game engine will handle as "standard" load for every race.
The thing is, consoles (the PS3) is not a PC. And Polyphony just couldn't design the game one way for 2D and another way for 3D. Same as they couldn't/wouldn't design the game to run one way with 12 premium cars racing and run another way with 6 premium cars and 6 standard cars racing.
I'm sure their current engine could handle way better aliasing, way better shadowing, a lot more textures and polygons for scenery and sidetrack audiences, particle effects (weather, dust), track detail etc, and even full dynamic damage-modeling, BUT not with 12 high-detail modeled cars. If the PS3 functioned kinda like a PC, you could adjust the alias and scenery detail to maximum settings (showing rich environments, perfect shadows, etc) for those races were you are "only" racing a few premium cars (lots of polygons and detail) amidst a whole bunch of standard cars (low poly, low texture, limited damage modeling).
But console games can't be designed like that of course and developers have to work for the lowest common denominator, meaning that even if the game engine is running quite light and loose during races 'cause you're not playing in 3D, or playing mostly with standard cars, you can't boost the performance in other aspects. And since I doubt they will go down from 16/12 cars or make the next game 720p only (which they should), I think the less evil solution would be to forget entirely about Stereoscopic 3D.
