Is a longer and healthier old age leading to unemployment?

So I was reading this article on msnbc http://www.msnbc.msn.com/id/32089674/ns/business-personal_finance and I got to thinking, should people who don't have a very rare and particularized skill and have enough money to retire be made to retire?

The article states that many people choose to continue working for several reasons after they retire and obviously if they need the money they should be allowed to but what about those who can? Are they not helping to keep someone else unemployed?

Here is my rationale. Person of retirement age X is most probably not in an entry-level position and so maybe a new person won't start off at their level but if someone in the company, say Q who is at entry-level is promoted then unemployed person Y could apply for and possible get Q's job. Thus, creating one less unemployed person.

If a mass number of X's decided to just volunteer their time to non-profit organizations and left their paying jobs, then Q's could move up the ladder in their jobs, make more money which would put more money back into the economy. More than likey X's aren't spending that much money on consumer products and stuff for kids because they don't need them and don't have young kids anymore. So Q is putting more money back into the economy.

Then we have Y, who didn't have a job and was maybe living off the state. They then have a job and so aren't taking money from the state and they are putting back into the economy with their new job.

This cycle has the potential to be really really effective. I am starting to think that maybe retired people who are just working because they have nothing better to do should think about how their actions may be affecting others who are coming up and want to work.