Standard Disclaimer (No one really knows at this point what the recovery will look like, this is simply an educated guess)
As of early May, JetBlue was showing some deliveries over the next year and a half. These expected deliveries have been reflected in the model, tied to the retirement of the E190 aircraft over the next two years.
JetBlue currently has 185 of their 265 aircraft parked, but it is expected some of those aircraft will slowly come back over the next year as demand picks up, making it difficult to forecast how many aircraft will be parked for the long term. This model simply assumes the 60 E190 aircraft will go as the airline starts to make the transition to the A220 fleet.

Photo by Ramon Kagie on Unsplash
Even though the model doesn’t reflect it some of the A320 aircraft may remain grounded for longer than the next few months, but it begs the question of why would the airline continue to take deliveries of the A321 NEO while keeping much of the A321 fleet grounded? (currently, 52 of those aircraft are parked) Unless they expect to have them back operational sometime next year in which case the E190 fleet would take the bulk of the seat mile reductions.
The model assumes, no early retirements(which are very possible) and that the pilot/aircraft ratio remains close to the same.
JetBlue Pilot Demand Model