There's still enough increases on other routes to keep slow growth of around 2-3% going for S19 I reckon. W19/20 is certainly looking challenging at this stage, likely to be largely flat at best. I think there's a good chance STN will return once the MAX issues are resolved and deliveries start rolling in to FR...
No surprise on NYC, there's under capacity on that route during peak summer now given it's lost 3x daily flights in the past couple of years. Supply/demand is a balancing act. I do think there were too many seats, but I now believe it's gone too far in the other direction. Why no wide bodies? DL have chosen to add BOS, and UA are still establishing IAD, instead of putting more capacity on NYC at this stage.
It would come as no surprise to me to see EWR/JFK upgraded to larger aircraft over the next couple of years when DL/UA are next ready to review capacity at EDI. With UA now sending B767s to LIS and MAN, I believe EDI is the only year round EWR route still on B757. With that in mind I'd say it's a matter of when, not if. DL have already used B763s a couple of times this season, not sure if due to pax loads though.