There is comfort to be taken from a new study which shows that even cities which are losing population can attract empty nesters and yuppies. These will be cities organized around consumption as much as production.
But the hope they offer should be tempered by the recognition that the newcomers can settle in, in part, because being childless, they are far less dependent on the services cities are supposed to provide. San Francisco looks like the future.

Aging industrial cities get boost: Population falls, but residents' income rising In Cleveland, Buffalo, Milwaukee, Pittsburgh and St. Louis …planning professors William Lucy and David Phillips (have found that while) population declined from 2000 to 2004, the per-capita income of residents went up slightly compared with those in the suburbs. (They explain that when) a family of six with an annual household income of $65,000 moves from the city to the suburbs and a single, young professional who earns $80,000 moves in, the city ends up with five fewer people who need government services while the per-capita income of that household soars. Places, they explain, have lost population, but it doesn't mean they're out of business. It gives them a chance to redefine what they are.”