A long time ago, in a job far far away, I worked with urban planners. I worked with them for some years. One thing I learned is that they absolutely and completely and totally detest the outer suburbs, and everyone living in them. Everything more than 15km from the CBD is a leper colony as far as they are concerned.
During my time interacting with them, they tried to cook up all sorts of wheezes, ruses and stratagems to keep people away from what they wanted - ie, a free standing house of good size on a quarter acre block. The planners managed to lock up plenty of land on the urban fringe, and they invented all sorts of taxes and levies that buyers of fresh blocks had to pay in order to provide "infrastructure".
One of the stated reasons for their disdain, hatred and disgust was the infernal combustion engine. The planners hate the air pollution that it creates, the time people "lose" sitting in traffic congestion and of course oil consumption. All that is bad. Bad, bad, bad. You are so naughty if you prefer not to live in a rabbit hutch, jammed cheek by jowl with your loud, stinky neighbours.
So I have this question for the black-clad urban planning brigades:
Let's say that solar power becomes wonderously cheap and electric cars become workable and affordable. Both technologies become so cheap, people choose of their own accord to move away from the infernal consumption engine towards small, non-polluting, quiet electric cars. We also prefer to buy "smart" cars that can self drive a foot behind the car in front, allowing much higher traffic densities, thus eliminating a lot of congestion. In essence, we would travel in "trains" consisting of our own personal transport, where we wouldn't have to interact with the Great Unwashed.
Doing so eliminates all the problems that planners hate about sprawl. It even introduces a word they love - "train". If we reach that point, will they still vociferously object to McMansions and large blocks on the urban fringe, because they have been trained to do so reflexively; or will they accept the stated preferences of the market, and shut the fuck up?