I'll bet we'll see additional Caribbean destinations although not as many as in 2009.

Service to Port of Spain from JFK has been kicked around for a while and fits Jetblue's target of a tourist destination but with some VFR traffic.
Hopefully, B6 will continue to add international flights from Orlando.
Belize City, Mexico City and Panama City would be excellent additions using the E190 although Mexico City may have to use the A320 due to their higher altitude. Delta pulled MCO-Mexico City a few years ago and only Aeromexico and Mexicana fly this route. Copa flies MCO-Panama City at least twice daily.
TACA recently began MCO-San Salvador although that market might be better served via FLL (no Spirit Airlines competition yet).

In terms of new routes between existing cities, MCO-Santiago with the E190 comes to mind as that area of DR is fairly affluent. MCO-Kingston also comes to mind. FLL-Montego Bay and/or Kingston could begin to eat some more of Spirit's lunch.

While I'd like to see service to Philadelphia too, Southwest would likely jump on BOS-PHL if Jetblue added that and kill their margins although apparently B6 is holding it's own at BWI?

Other domestic cities that I think would fit nicely within B6's network are Hartford to Florida flights. Jetblue's got some brand recognition in the area through White Plains and Boston and could possibly drive Delta out of it's niche there as B6 did to FL at White Plains. Key West also seems to fit within B6's network with flights to FLL and/or Orlando. Airtran began 4X weekly flights to Orlando recently but Jetblue could add daily flights with the E190.

Also, I'd love to see some backfilling in LAS with US Airways pulling up the stakes but that doesn't appear very likely.