I was told that the average NJA pilot age is in the mid 50s. I don't know if that's true, but if so that means about 1/2 of the seniority list will be gone in 10-15 regardless of resignation (the average pilot loses 1st class medical privileges in their late 60s) or potential mandatory retirement age.
NJA will have it's movement too. It's just now is not the time. There is little doubt the majors will furlough and take concessions again in the future. This is a cyclical industry that is in need of competition.