United had pulled out of JFK in 2015, but just recently came back, because it turned out JFK's "prestige" factor impacted their business. EWR is a major United hub, but the idea of EWR being blessed with the "prestige" of supersonic flight is a bit funny.
Although I wouldn't be surprised if it gets moved to JFK as United rebuilds their operation there. A lot can happen in 8 years.