Lawns are a social obligation. Most people really wouldn't miss them,
especially if the garden that replaces it produces yummy vegetables.
Kids need space to play, but that can be edible landscaping instead of grass.

Roof gardens will likely become more popular as well.
These are an option even in the densest urban settings,
and they can significantly increase the cultivatable space in the suburbs.
All that dirt on the roof would provide quite a bit of insulation, and
capture waste heat from the house, possibly extending the growing season.