On the Raise The Hammer site, Polycarpou has written a set of scenarios that deal mainly with impact on suburbia of "peak oil": the idea that oil is a finite resource and that we are using oil faster than we are discovering new reserves. Having examined scenarios that mainly focus on the impact of peak oil on suburbia, Polycarpou suggests the following conclusions:
Even with oil supplies in decline, it seems at least plausible that a great portion of the resources now spent building sprawl could be diverted to retrofitting and revitalizing suburbia.
If, instead of building more spread out, single use neighborhoods and strip-malls, we used our current building energy for infill development (using principles of density, walkability and mixed use currently associated with "New Urbanism" but known since Jane Jacobs wrote The Death and Life of Great American Cities in 1961), we could begin generating an ever-more efficient economy, and perhaps stretch out the tail of oil depletion.
The highest priority, then, should be to stop current and future sprawl development.