The atr and saabs, and soon dash2s are too expensive due to heavy checks. By 2017 if not sooner pdt 200s will join the eagle atr and clgan saabs in the scrap yard. Source, union work and that's flat out managements view.
Add in low gas prices, pax hate them, pilot pay shortage, and endless supply of 50 seat jets paid off. The q400 doesn't work in the USA, you won't see it besides horizon where it actually works.