I say "could" instead of "will" because all this is more a question of cultural development than a technological/economic one. If individual car usage does not go out of fashion, robotic driving will only continue the trend towards ever bigger commuter castles.
What does that mean? Like someone from the victorian age? I think they are all dead.
Also with more people using it, the less meandering it does. If everyone uses the "uberpool" system, it will probably pick up everyone in about 5 minutes in a 2 block radius and drop you off at one spot 1 block from your work. The more dense it is, the more efficient it gets.
And if 1 occupant per 2-ton-vehicle becomes the norm, dense cities will implement congestion pricing or surtaxes to force multiple occupancy or public transport usage - if 1 million driverless taxis try to deliver people into the square mile of the City of London, everyone will have a bad time. (Ditto for Manhattan, SF, downtown Boston, Hong Kong Midtown etc.)
The other factor is school. While I can show up at work, more less, whenever I want, my daughter has be at school by 8.10 at the latest, as does everybody else's kids. If we don't add flexibility to school starting times times then, to many people, it won't matter what sort of flexibility they have with work.
Not all Americans are atomized urbanites. Many are in families.
My MiL, wife, myself, and my two kids could easily share one self driving car although the number of miles traveled would likely be staggering.
If my kids destroy "dads car" they are in big trouble, and "dads car" has "car alexa" and she will yell at them for awhile if they misbehave and god help them if "car alexa" has to resort to facetime dad at work to mediate a child argument. "Wait until your father gets home" worked on gen-xers when they were kids, but now we have facetime and dozens of equivalent systems.
The mileage used and CO2 footprint will likely be much higher than individually owned cars because every trip everyone takes will be twice as long upfront, plus my kids will be car mobile which means much less sitting at home (Hey, you want your allowance, have the car drive you 10 miles to grandma's house and rake her leaves while mom and dad at work and behave yourself because Car Alexa has her eye on you and I will ask her). Also my senior citizen MiL would never road trip at her age and driving ability but a self driving car would result in a lot of visiting rural relatives and doing stuff in the hypercongested and terrifying to drive in downtown. Heck if I had the car at my beck and call why would I ever eat lunch at my desk when I could hang out at a nice park instead and never care about parking or driving. Hey why drive the whole family to the library when you can just send all four separately at their convenience, each of which takes twice as many miles because its pick up and drop off service unless no one else needs it, for 8 times the number of miles driven. I need a head of lettuce for dinner tomorrow, normally I'd get it on the way home from work for "free" ecologically speaking, but my son is just doing homework on his ipad so I'll send him out shopping on a special trip because he can do his math homework for 90% of the time while the car is driving him.
I would realistically estimate we're doing about 25000 miles per year across three cars and if we replaced it with one extended family self driver, I think it quite reasonable we'd knock out 60000 miles per year. Given that the self driver is likely to be staggeringly more expensive than any of our three cars, it probably cheaper and better for the environment to have separate cars, at least until self driving is so cheap its "free".
I ask as someone who doesn't own and doesn't want to own a car. Where I live, public transport is good, and even taking a Taxi everyday is cheaper than car ownership if you only use it for your commute (not by much, but it's competitive). Still people love to own and use their cars. I would love to see people share them, but I fail to see how self-driving would be an incentive for that.
1. Much higher occupancy per car. Based on my personal observations, at rush hour the average occupancy of a car is something like 1.3. I don't see any reason that can't increase to 2.6 or more without significantly slowing anyone down -- 2x
2. Yes, a lot of people need to get to work at 8, but normal working hours start at different times for different people, anywhere from 6:30-9:30 is fairly typical in a U.S. city. If the average person has a 30-40 minute commute, and there is a reasonable amount of reverse commute demand, a car should be able to make 2-3 round trips per day at least -- 2.5x
3. Cars driving more efficiently with quicker reaction time and less mistakes will speed up commutes a lot. Hard to say how much but I'd say at least 30%. This directly increases capacity, since shorter commutes mean each car moves more people in the 6:30-9:30 window -- 1.3x
4. If self driving cars can communicate with each other to park, they can pack themselves very closely, and make room for a car to get in and out, removing the need for oversized parking spots, space between cars for doors to open, and aisles between cars. This should improve parking density by at least 3x.
5. Cars that are on-demand and self-driving can be smaller than typical cars we drive today. Since you can order any sized vehicle based on what's needed for an individual trip, there will be many fewer empty seats. Without the need for a steering wheel and controls, interiors can make much greater use of available interior space. This should reduce the exterior size of the average car at least 1.5x.
6. Cars can find parking in more remote areas. If parking is not available within a block of the office, the car can drop you off and park a few blocks away. This increases utilitzation, say 1.2x.
So, multiply it all together, and you get 35x better parking efficiency. It's going to be a huge win for dense cities.