Re: not until after a long, long, *long* period of mixed autonomous/manual traffic
I generally agree, though this is a huge cultural shift so I believe autonomous cars will have to demonstrate very good safety performance. But as you said, the great saving of human lives and insurance money, *AND* vehicle and petrol cost reduction will be overwhelming factors in bulldozing their adoption. Around 5 years away, like all the automakers say.
Finally, there is the terrific and generally ignored power of networked sensors on vehicles. An auto vehicle will likely have 3-4 complementary systems for navigation and safety. But the biggest safety improvement, at least on fast and/or busy roads, is the hundreds or thousands of sensors working together to avoid conflict and tragedy. That means cars will talk with cars, with roadside sensors, with pedestrians' (especially children's and pet's) wearable sensors and smart logic, and all that will work together to make driving as safe as it can be.
When that coordinating software and hardware is mature enough, the revolution will begin. I, for one, welcome our...
...(Mine's the one with the Lewis Hamilton patch.)