Except that's not it.

The problem will get bigger and bigger, requiring more and more compute power. You see, whatever system you design to autonomously control a car will never be "enough", or perfectly safe. There are simply too many variables in the environment, too many possibilities. So a certain design, taking a certain amount of compute power, will give you a certain level of safety. But it won't be perfect. People will want more safety and better systems. That'll take more power (probably exponentially more, as we've already seen with other simulations). The cycle will never end.