This higher income move back to the cities can be a good thing when done with the appropriate dose of urban planning. The trick is to arrange a tight-knit area into stratas, where there is a seperation of income, but only a subtle one, to ensure an almost-equal opportunity to access the needs of the entire community. Developments which create sharp divisions without a multi-tiered approach can form tensions that are often seen in cities such as Chicago, or D.C., where gentrification does not deserve the euphamism 'urban renewal' because of its lack of a holistic approach.
The mixed income communities that I have seen in Vancouver and Toronto leave me surprised to know that they continue to exist. The concept is good, but up front it appears too idealistic. I wonder if there are incentives that are made to influence the upper tier into moving into such a neighborhood. Maybe there are such incentives. Does anyone know how those communities really work?