Urban shrinkage is a factor that widely addresses the scale of regions and requires policy-makers to redefine traditional paths of regional governance. It can be observed that especially in the US, planning practice is to a large extent concentrated on either managing urban growth or tackling redevelopment in a fragmented – not a regional – way. The search of the notions of progressive regionalism should deal with the problematic of shrinking cities. This could offer a window of opportunity to discuss a shift in paradigm from growth-centered planning to more sustainable regional development patterns and thus be of value for a stimulation respectively redefinition of regional governance in the US and in further countries.
You can find more on Pallagst's work here and here. Pittsburgh's strategy to deal with shrinkage is characterized as a "revitalization of the city center." But the efforts are failing and Pallagst wonders if Pittsburgh will now engage in a regional approach. Meanwhile, Youngstown is embracing its declining population and attempting to scale-up efforts to the regional level.
A post over at Null Space does indicate regionalism afoot in Pittsburgh. However, I'm skeptical that an attempt to cultivate a regional identity will work. I think the city should focus its efforts on its connections to places outside of the region.