Well... depending on who you source, the majority of people already live in urban environments. In the US, the most recent figure from the census is 62.7%, which is more narrowly defined at % of population living in cities[1]. If you count "urban areas" which includes towns and villages, it is north of 80% [2]

Worldwide, we are at ~54% living in cities. [3]

This trend seems to be continuing globally as well [4], so pretty soon people in non-urban environments may have no choice (assuming, as I do, that cars will get more expensive as they have more and better technology and are much more highly utilized due to sharing)

[1] http://www.census.gov/newsroom/press-releases/2015/cb15-33.h... [2] http://www.citylab.com/housing/2012/03/us-urban-population-w... [3] http://www.un.org/en/development/desa/news/population/world-... [4] https://esa.un.org/unpd/wup/publications/files/wup2014-highl... (page 7, Figure 2)