PDT will never get 175s. Why would AAG waste millions of dollars a month on training, maintenance, management, and other costs? AAG is wisely moving flying around based on fleet type to reduce costs and be more efficient. In the end, PSA will fly the CRJs, Envoy will fly the EJets, and PDT will fly the 145's.
Once the fuel prices rise again and the market tanks, the 50 seaters will find themselves parked in the desert somewhere.