The problem with Loyola and Northwestern is that the real estate value of the school's location was far more valuable then running the schools themselves. Property in those areas goes for $$$$$. Most dentists I know in the area either attended or highly regarded both schools and the dentists in the east coast also seem to have a fairly high regard for both schools.
As far as MWU, I've talked extensively with an OMS in the area who sits on the admissions committee for the DO school and he's very confident a new school will open in the next few years. In fact when I was applying for schools for 2007 admission, before MWU was made official, he was under the impression that the school was going to be opened at the Downer's Grove campus in Il. When it was announced that the school was to open in Arizona, he seemed shocked.
From what I understand, the MWU campuses aim to have most professional programs as well as a nursing program (if nursing is a professional program, sorry for naming it separately). So if having a dental, pharmacy, osteopathic, and nursing programs on one campus is the goal, don't be surprised to see one pop up in the DG area.