I think a lot will be persuaded to retire by circumstance. A lot of pilots on 4 engined fleets are looking at a lot longer than 6 months off work. For many it'll be closer to when replacement aircraft arrive, which could be until 2023 when the A350 arrives.
So if you're late 50's/early 60's, you're going to be looking at several years without flying before having to complete a full type rating and return to work for just a few years back in the F/Deck anyway. Will the time off spent on the farm/at the holiday house up the coast/doing the lap of honour in the caravan etc maybe convince them that red eyes/jet lag/sims is something for the younger crowd and to hang up the hat for good?