Don't rely on what phone agents tell you. Just take a peek at the B6 website.

We're waiving change/cancel fees for customers with existing bookings made through February 28, 2021. If you choose to rebook, you can do so on any flight through the end of our schedule. Fare difference may apply.
For voluntary cancellations, funds will be issued as a JetBlue Travel Bank Credit. JetBlue Vacations bookings will be issued as JetBlue Vacations Credit. Travel credits can be used for future travel to any JetBlue destination and for any traveler.

If you do book now for travel in December and then determine (outside the refund cancellation window) that you want to cancel, juts hold off until the day of travel. If B6 cancels or makes a substantial change, you are entitled to a refund. On the day of travel, if nothing has changed, you can cancel for a funny money credit and you are no worse off for having waited.