The attention to detail is stunning! There is no doubt premium models will be carried over to the next-generation version of Gran Turismo, but that does mean there are going to be some inconsistencies in quality. For instance, the premium models used in Gran Turismo HD and Prologue lack the detail Some GT5 and GT6 models have.
At least it is no where near as bad as the standard/premium issue in the current gen GT games.