GM, Ford and Chrysler are abandoning the sedan because no one wants to drive them and those that do are happy with a Camry or a Hyundai which are lower priced and about as maintenance free as it gets. Sales have been declining for several years in favor of pickups, SUVs and high end sedans. I remember when it was damn near an event to see a Maserati or a Bentley on the road and you knew it was someone famous, now you see them all over Houston. Why build something no one wants to buy?
Convincing individuals to give up the freedom of driving themselves will be a generational transition. I agree with three sides that it will be less than 10% in 20 years. It will be a balancing act for manufacturers of the vehicle and the components that make them autonomous. How much money do you spend on a product that no one wants to buy?
It's possible some states or even localities may mandate it somehow under the guise of relieving traffic congestion, cleaner air etc but that will be heavily challenged and logistically challenging.
The real money will be spent where the potential for returns is the greatest and that's in trucking. Imagine not having to stop a truck for drivers timing out on their DOT limits and not having to have driving teams. You can keep a truck moving 24 hours a day with no labor costs.
Dallas to Phoenix is 16 hours. A driver has to stop after 10 and rest 8 so that trip takes a full 24 hours. That same truck could be more thatn halfway back to Dallas if autonomous. Chicago to Seattle is double that. That's a money maker and that's why truck manufacturers from Paccar to Daimler and Volkswagon are all investing in the technology.
After a couple of generations of people seeing that the technology works and discovering how they can be productive while riding instead of driving then the cars may go that route. At some point only the rich will own sports cars and they will be kept and driven at special tracks like the one near Rosharon but we'll never see it that extreme in our lifetime.