JetBlue haven’t announced anything as they are campaigning hard for the Delta/Virgin/Airfrance group to be forced to give up Heathrow slots.
if the competition regulators rule they should the B6 will go to Heathrow. If they are unsuccessful then they will go either Gatwick or Stansted.
Gatwick is already well served on both NYC and BOS they could own the market at STN. The flip side is there is a proven market at Gatters.