I wouldn't wait for Delta to call you. Now that they've changed the flights, they will automatically assign you to new flights, which might not be at all convenient. The flights will fill up, and you might get shut out of the best times. Also, now that you're flights have been changed, so has the equipment, and you no longer have seat reservations.
Call now, do'nt wait for them to call you!!
And Jet Blue can't "just move in". Delta owns the gates and slots, they would have to want to seell them to jet Blue (doubtful) and get various approvals for same.
Anne