I've heard from others whose JetBlue flights from BOS have been changed to a connection through JFK. I've flown it a few times, and while it's not preferred, it's not that bad.

For those whose JetBlue flights are changed, double check the dates which you're rebooked for. It doesn't look like JetBlue is flying the JFK-SXM route on Saturdays, or Saturday flights are full, and some have found their flights changed to a Friday, and others have found their flight changed to a Sunday.