RE: New 50 seat CRJ? It is a good question, right now in my opinion most major airlines seem to have lost interest in 50 capacity market except maybe Eastern Europe. The major difficulty I see in the plan would be the actual age of the plane. It is an old model so I'm not sure what the life cycle would be for the airframe. I can see them being somewhat converted to private jets, but then they would be cutting into their bread and butter on the business jet side.
Not to sure if their is a new engine that would make it attractive to airlines, not to mention they have quite a few things on their plate for the next couple of years. But I see no reason if the demand were there say in the next decade and fuel prices stable that they couldn't make a case for it and bring back a new better version, but again I see airlines wanting less planes not more. Better to have one plane carry 75 people than two with 40. Plus we would need a new engine, not sure if any of the players are interested in that segment.
Who knows crazier things have happened.