Everybody would like to see their favorite route's 50-seaters replaced by 737s.
IMO, the chances are practically zero that RDU-JFK ever gets scheduled 738s. Ain't gonna happen.
Very slim chance that RDU-JFK ever gets A319s. Very good chance that most or all of the 50-seaters on that route are eventually replaced by 70-76 seat 2-class larger RJs as more and more 76-seaters are delivered.