First of all, you can't magically make a car HD. You can output at a higher resolution, but you'd just have a sharper version of the same thing. As absurd of an idea as it is, there CANNOT be 830 cars ported from GT4, as there were only 720 cars total in the game.
5 years is enough time to model 830 cars with poly counts around 200k. That is roughly one car every three and a half days, and we can be damn sure they have more than one person working on the models. Also, as Polyphony Digital claims to use laser scanning, it should be very possible to create 830 models in 5 years or even less.
If you look at rFactor and the recent progress on the WSGT 2 mod, extremely detailed cars are being modeled, rendered, and put in game almost bi-weekly. That is a few peoples hobby, not their full time job. You can check that mods progress
here if anyone has doubts.
Every car in Gran Turismo 5 will have full interiors and be completely new models. If I'm wrong, I'll eat my shoe.
physics can't even hold a candle to iRacing and rFactor. I was elated to read that there is an entirely new physics engine.
