"Many low-density suburbs and McMansion subdivisions, including some that are lovely and affluent today, may become what inner cities became in the 1960s and '70s -- slums characterized by poverty, crime and decay,"

No, they won't, because unlike cities where you can always mug and scavenge, and there's the option of walking or biking, exurbs are useless unless you can grow your own food and hunt. And the McMansions weren't built to last, so they'll start falling apart within a few years.

If the middle classes can't afford to live in them, poor people certainly won't be able to. They probably won't even be able to afford to squat in them.