Seconding shakethemonkey's comments and would ask: how much thought do people put into the car they buy versus the cars they rent?

The car companies have enjoyed brand loyalty and the ability to sell feature bundles because many people associate their car with their identity. When you say “Mustang owner”, “Subaru driver”, etc. specific images come to mind, and across all cars you see things like people paying considerably more to e.g. have a fuel-inefficient engine because there are a few times where they can step on the gas and enjoy the rapid acceleration. Manufacturers made billions selling SUVs to people who thought safer, cheaper minivans were too boring.

That doesn't completely go away with self-driving cars – someone with 4 kids will still have different needs than the avid bicyclist or single urbanite — but a lot of it will become less important if people start thinking about their car as, say, the place where they play games or catch up on Netflix while they head home from work. Why pay Ford for the premium sport package when you can put the money into a faster mobile data plan or a better tablet? They certainly don't go out of business in that scenario but the business becomes tighter and less exciting if it becomes more of a commodity where people generally just buy whatever's cheaper.

Self-driving cars drastically reduce the total number of cars necessary, and, as the article notes, limit the ability of manufacturers to upsell features. If the fleet of cars on the road were largely self-driving, there is no way it would support the present variety of car manufacturers. I would hazard that most would go bankrupt.