I don't see too much difference between "standard" and "premium." I'm not really a car freak, so I'm probably more like the guy on the street. I'm sure when I get the game, I'll enjoy the ride for what it is, and hardly recognize the difference between the two. Heck, I've seen that screenshot of the standard prototype, and couldn't point out the difference.
That is why if the two are separated, I'll probably shy away from the game. What's the point of having over 1,000 cars if everybody drives the same 200 online? I know 200 is still a lot, but it's going to get boring for a lot of people, and then where else do you go? What if some want to race standards and some premiums? It just doesn't make sense that PD would go all though getting a thousand or more cars in the game, and then having "tiers" for them to race separately.
"Let them race together" is what I say. Enjoy it for what it is, a game/simulation; not real life.