Urban area crime reduction starting around the 90s led to most movement back. The dual income job requirements just make it stickier and create a feedback system of higher housing prices. (which require more dual incomes...)
As soon as that dual income want kids and can afford it on a signal income in suburbia, they'll take it most of the time.
When I graduated grad school in the late 80s, almost no one I knew went to live in an urban core other than a fair number of NYC finance folks--and few of the non-finance jobs were in a city proper. Even the New Yorkers, almost everyone migrated out to suburbs over time. I think I knew maybe one couple who stayed in Manhattan.
As soon as that dual income want kids and can afford it on a signal income in suburbia, they'll take it most of the time.
Just my .02