And the Sims 4 isn't going to get an open world because it was built on an entirely different engine than TS3.
Also in TS4 there are some neighborhoods (like the Vampires GP's neighborhood of Forgotten Hollow) that don't have real streets, so cars wouldn't work in those neighborhoods without completely changing them. There really wouldn't be much driving, just our Sims getting into a car and it backing out of the driveway before disappearing and getting a loading screen like cars did in the Sims 2. This is because there isn't a real use for car without an open world like the Sims 3 had. while it is possible that the Sims 4 could get moving cars in the future, it isn't probable.