I didn't mean to suggest otherwise, sure, it will start with 'highway mode', but that won't be a long phase. For obvious reasons people will desire the ability to drive on surface roads. Actually parking will come before surface roads, Ford already has a system that can autonomously move the car and park it, driving at low speeds in a dense environment. It will only be a matter of time, I still say about 5 years, before these capabilities have effectively merged and we have a car that can deal with most situations. It might not be allowed to just drive without a 'supervisor' for a certain time, but there will be a huge push to get rid of that limitation.
Think about it, an autonomous car can go to school and pick up the kids, it can go to the store and be loaded with groceries, it can go to the dealer and get maintained, it can come and fetch you, obviating the need for a second car in many cases, etc etc etc. People may think they want to drive right now, but really they don't. They want the power and convenience of instant effortless transportation.
And once that day comes, then they won't even care about owning a car, the concept will be silly. The entire edifice of the car culture will vanish like a puff of smoke into nothing. Cars will simply become a ubiquitous utility, a service you pay to access and which supplies you with however much personal transportation you need or can afford. And of course then it can be supplied at different grades, you can ride with other people going where you're going and its cheaper, you can ride a 'car' that stops at various stops and picks up and drops off lots of people, gosh its a bus! Everything is about to change. The entire edifice upon which most people's reasoning about autonomous vehicles is built will be quaint nostalgia in 20 years.