Our evolution as a civilization has always been related to our ability to mobilize people and goods; and for the same reason, the future development of transport will notably mark our evolution as a society.
Before answering, it is important to distinguish what kind of cities we are talking about. North American cities, which to date have bet a lot for the car and the suburbs. European cities, which have been oriented more towards densification and public transport. Or giant cities, and some new ones in Asia, which are sometimes built almost overnight, and contain more than 10 million inhabitants.