I think what he means is that there will come a point at which technology renders most occupations obsolete. What happens when 90% of the population aren't needed in the workforce?
They do something else, as the said 90% of agricultural workers did during the industrial revolution, as did typesetters in the 80s, as did computers (the profession) when computers (the machines) took over.
Human desires are endless. This is why you will always have employment. Technology frees up time and humans than use part of that time for leisure and part of it for doing more meaningful, higher value work.
What do you mean by "employment"? In the far enough future, anything that's deemed profitable can be done much faster by automation. No one will pay a human a check to do something that can be done dirt cheap by a robot.
The point is that our society rations limited resources through money. When resources are no longer limited, and no one can earn any money through employment, we'll require a completely different social and economic system for distributing resources.
I don't think that will happen until we have "replicators". Until we can make literally everything ourselves, we'll still need jobs. We'll also need almost limitless resources, too, unless our desires will tend more and more towards virtual things rather than physical. Either way, it's really hard to predict what will happen 50 years from now, but I'm quite optimistic about the human race.
