Ok, disregard some of my comments. I haven't played GT5 since early 2011. Updates have apparently allowed for changing wheels and have even improved the quality of standards somewhat. Given the fact that Polyphony have done this, I think they have a team working on greatly improving the standard models. They may not model interiors, and instead they could end up using a generic interior, but I get the feeling that most standard cars will be ported and they will be of a greatly increased quality compared to their PS2/PSP counterparts or original GT5 counterparts. Some may get the full premium treatment like the Countach LP400 which featured in the promo video. It was previously a standard car.
I just hope they get smarter with the duplicated cars at least. If they model one R32, R33, R34 skyline, why can't all sub-models be premium? Sometimes there are no visual differences, other times, they are small enough to add in an hour or so, surely. Also, speaking of the Countach earlier. Surely, modelling some wheels, flares, some different vents and a wing to make it an LP500/QV5000 would be easy enough? I just hope they actually think about how easily they could flesh out the premiums this time. Sure, I get it that some people hate the duplicate cars. But given how little time it takes to alter one model into 2-5+, I think it's worth it for those who have their preferences within a model, or own/owned a particular model/year of the car.