I'd like cars in the game. I won't be sad if we never get them, but I'd like them. I'm actually neutral on drivable or not. It would be cool in some worlds, but others just aren't set up for it (or only parts are) and I can see some reasons why having drivable cars wouldn't be practical.
But if we get them, they have to at least have parked interactions, because otherwise I can just go into Debug and use the ones we already have in game if they're just decor. Let our sims fix them up, soup them up, wash them, woo hoo in them, and use them as a means of opening the world map, and I'll be perfectly content.
Being able to enter a kind of "create a car" and detail them would be a very cool bonus, but I'm so not holding my breath. (But oh, the 80s rocker vans...)