Republic has proven itself to be a disaster. They forced the hands of the legacy carriers with the bankruptcy, demanding more money. It only worked because they really needed the lift that rjet is currently providing. That lift will not be needed forever.
The question is, however, what will happen moving forward. United is buying 737's and will eventually phase most of the flying out. Delta is also phasing out a good percentage of it's regional flying. AA has doubled down on its WO, and is trying to grow them so it can cut back on contract carriers.
RJET forced the hands of the legacy carriers, but they will get the last laugh.