First, welcome to JetBlue. I have only been at JetBlue for four months on the A320. I am ex-military, too. I recommend contacting the People Department/Pilot Hiring if you have questions. You may have already done that, but they were very informative and quick to respond to my issues when I transitioned. Its a good pilot recruitment team here. Its also a strong pilot group. You'll like the personalities on the flight deck.

I separated (not retired) from the USMC. I had similar challenges when I left 5 months ago. My airline job sit was not settled when I separated. I have a reserve flying job so I didn't change my timeline. I would have picked time up at the reserve job if I needed it. If you are only separating, its a fairly small commitment to the military to keep "weekend warrior" affiliation and it certainly has its immediate benefits in this chaotic industry.

As for the fall, I have not heard/read about a date for new-hire class resumption. Unfortunately, I imagine the company will evaluate the summer market conditions and competition before assigning new training dates. There are B6 guys on this board, though, who are much more in the know than me. Good luck.