They also left SDQ and then came back and now SDQ is the star performer of their system. Here are all the midwest cities they don't serve and probably should serve:
IND
CMH
CVG
STL
MCI
MKE
What do they all have in common? They are all medium sized markets within LGA perimeter that have hard time supporting JFK service without TATL connections and are not large markets from BOS. Now that they are also building up EWR and LAX and have more slots JFK, it would be easier to open these stations. Just look at MIA, they were able to open the station with 14 flights to 4 airports right from the get go.

Outside of those midwest airports, the only airports they are missing from top 60 in USA are
https://en.wikipedia.org/wiki/List_o..._United_States
IAD, MDW, HNL, DAL, OAK, SNA, SAT, OGG, ANC
All these airports are either not in continental USA or are not the primary airport in their area or dominated by their neighbor city (SAT).

So hopefully they do add most of those missing midwest cities over the next few years.