A couple interesting pieces on immigration worth reading together (the comments to the first piece have some interesting thoughts and information; conversely you can ignore the national-politics elements in the second piece, which are not relevant to the point I want to make):
http://nullspace2.blogspot.com/2014/07/pittsburgh-immigration-stats-update.html
http://fivethirtyeight.com/features/immigration-is-changing-much-more-than-the-immigration-debate/
My suggested takeaway (which is admittedly an old hypothesis of mine):
The Pittsburgh region has essentially missed out on the Latin American immigration wave, which has died off in recent years and probably isn't coming back to anything like prior peak levels. Latin American immigrants are spreading out a bit, but not fast enough to make a huge difference here. We'll probably gradually get more people with some sort of Latin American heritage in coming decades, but they will increasingly be native-born citizens, English-speaking, and mixed-heritage.
On the other hand, Pittsburgh may be well-positioned to get its fair share of the growing Asian immigration wave, maybe even a bit more than its fair share. And that is a good thing, because for the most part those immigrants are going to bring some valuable combination of education, skills, ideas, and/or entrepreneurship. And all that will have an influence on things like the location and nature of future potential demand for new development.