There are so many things I can think of. The taxi/rental/on demand model is far more likely to happen because who needs to own a car 100% of the time. Ride sharing is also easier - I suspect many people would be happy going a few minutes out of their way for halving the cost of their journey. (Computer systems would automatically manage supply and matching demand, as well as pricing.)
Not only do you need less parking for fewer cars, but you could have less parking for the same number of cars. For example there is no need for stores to have huge car parks - customer and employee cars can go and wait somewhere else and only return to the front door just as you come out with your goods. This can lead to far denser human centric areas.
Some roads can actually be decommissioned. Vehicles can load balance across existing alternatives and respond far quicker to developing bottlenecks. Occupied vehicles can be given priority over shorter routes than non-occupied ones.
Deliveries can be done without drivers. For example the delivery vehicle can drive to your home, work or anywhere else and you enter a code to get your items vending machine style.
It will give people greater freedom. For example if your vision isn't acceptable, or you have physical issues then it won't matter. In general the maladies that come with age won't affect mobility anywhere near as much as they do today.
Drives can be over longer distances as there is no driver fatigue. Perhaps there could be sleeper cars for when you want to go somewhere overnight.
Heck they can even do things like deal with you in the vehicle while you are driving to an airport or a border. You could show your passport, answer questions, check luggage etc. And then go straight through the border or walk straight to your gate at airport, or even be driven to a closer access point to the gate.
And I suspect we never get flying cars out of this. When the two dimensional earth surface is used so much more efficiently, why expand into 3 dimensions? And since we can increase the speed the more vehicles are automated, what advantage does flight have?