What Happens When the Competent Opt Out?

By this terminal stage, the competent have been driven out, quit or burned out.

What happens with the competent retire, burn out or opt out? It's a question few bother to ask because the base assumption is that there is an essentially limitless pool of competent people who can be tapped or trained to replace those who retire, burn out or opt out, i.e. quit in favor of a lifestyle that doesn't require much in the way of income or st…