We're going to see more high-density construction occur in the next few decades regardless of planning. As people get older, they become less mobile and as a result might demand more services closer to where they live and to which they can walk to. A large portion of this country is going to be retiring within the next decade or so, and those people won't have as much energy to put towards maintaining a regular home.

There is a 30-story retirement community planned for the South Waterfront district, featuring over 200 residences, plus assisted living units and staff housing, as well as health services recreational amenities.

See:
http://www.mirabellaretirement.org/portland/

(Update: I may have misread the part about staff housing somewhere, I don't see it in the company's press release, so please disregard.)