FR have publically stated that SNN is a concern for them, with results well short of expectations. Now, if FR can not make SNN work, then I cant see other carriers making it work. I am sure SNN can sustain an FR base in the long term, but perhaps with three aircraft, as opposed to the current 4.
SNN's troop traffic has all but evaporated - more revenue lost.
T/A flights are also decimated, with ORD likely to be lost from EI.
In the long term:
JFK - EI / DL
BOS - EI
EWR - CO
ATL - DL/seasonal.
Still a very impressive list for an airport the size of SNN.
Brian.