I think the mistake here is single-issue activism. The problem is that people are being forced to consider extended working because existing pension provision is too poor. The answer isn't extended working, it's better and more flexible pension provision.
People who will receive 30-50% pensions are going to be much less interested in extended working than people who will be forced into poverty even though they've been working since 18 or 21.
A basic thing to always remember, as Coluche said, is that people don't need work, they need money.
As for the problems our societies so atomised that the only way to have social relationships (and socially recognised value) is through employment, well, that's one for another thread. Possibly a much more important ones.
However I looked recently at death age tables and didn't notice any uptick after retirement age - probability of death was rising exponentially from 20 to 70, and getting significant right around 55. Do people die a few years after retiring, or do we interpret deaths that happen right after retirement as caused by inactivity ? Un roi sans divertissement est un homme plein de misères