True but assuming the future is that of mostly robo-taxi companies (and not individually owned self-driving cars), there will tremendous business pressure on robo-taxi companies to make their cars as efficient as possible, as the cost of gas (or other energy) will be part of their cost of providing the service.

Today car companies sell cars based on many criteria. Fuel efficiency is one of them but when gas prices aren't too high, individual customers don't care about that very much.

Someone who operates a fleet of 10.000 cars will make fuel efficiency their top-most priority because that will drive down the cost of their service and the cost will be a major reason why customers will pick one provider over another, not how stylish the car is or how fast it goes from 0 to 60.

E.g. if they realize that by putting solar panel on the roof of the car they can save money in the long term, they'll immediately put solar panel in every car. The progress in making cars more efficient will be much faster.