CALFO;
They are already flying inefficient trips. There won't be enough 80 hour months to go around. There simply won't be enough block hours.
Yes, some of the Captains will retire straight out of the 75 fleet. But most of the pilots will not. Bumping gives you a paid move, free PS commuter passes, and no training freeze. Few will bid off until they gut bumped. I wouldn't.
400 retirements a year is only 3% of our pilot group. This is nowhere near "massive". Just "normal". 3% a year for 33 years equals? All of us. This is simply a normal rate of retirement.