Considering the fact that GT5 isn't exactly hard to top, GT6 may very well be the best Gran Turismo game to date. However, it'll still be lagging behind everyone else in certain and important areas, sadly.
As it looks now, even with a lot of the much welcomed improvments, GT6 will still be suffering from the same issues that GT5 had and will once again miss the community's most requested feature(s).
Although PD are clearly trying their best to demolish the lines between premium and standard cars, the visual inconsistency will still remain. Features such as a livery editor has yet to see the light of day, not to mention drivetrain and engine swaps which have been one of the main attractions when making hybrids. And sounds, well, let's just not go there.
They're getting there, or at least it seems like it, but it's all happening at the speed of a snail.