The thing is - self-driving cars fundamentally change the structure of the automobile market in a way that negates many of the advantages of existing automakers. Instead of private ownership of cars, they encourage ride-sharing services, because the car can pick up a different passenger on the return trip and no longer has to park. Instead of internal combustion engines, they encourage EVs, both because of the power-draw of the self-driving hardware and because refueling becomes the responsibility of the service, which can program them to return to base and not pick up any new passengers once they're getting low on charge. Instead of servicing being a huge pain that encourages buyers to put a premium on reliable cars, maintenance is handled by a centralized maintenance department full of professionals. Instead of family cars, they encourage small motorcycle-like "pods" sized for a single occupant (with a smaller number of family cars or trucks available for family trips).

Already, that negates the advantages of consumer brand, reliability, dealer networks, internal combustion engines, ergonomics, and bodywork. There's not all that much left to the auto industry, once all that changes.