I'd like to see Salt Lake become not physically larger, it's already very sprawling, but much denser in the core. The existing downtown is nice, but relatively small. The same goes for Albuquerque. I wouldn't mind seeing Boise, Madison or Spokane grow either. As a whole though, I would rather the population grow into depopulated, abandoned urban areas (the Detroit's of America- Detroit being a place I would like to see grow to prominence beyond the automotive industry) before much more expansion outward happens.
To the OP-I'm glad you like Pennsylvania, It is one of my favorite states as well(along with Colorado, Oregon, Massachusetts and Vermont-I like mountains
(and the rockier tendency of New England's and the PNW shoreline)). It would be nice if Pittsburgh would play a larger national role again, it definitely has the potential and the added bonus of a stunning natural setting.