Technological advancement has already taken over or eliminated certain job sectors. I remember mechanical looms and the invention of the calculating machine.
And it's something that will continue to happen, at an ever-increasing pace.

Of course, new jobs will emerge; the problem is that it's difficult to re-adapt or reinvent oneself quickly enough.
Unemployed people will be frustrated; their experience and knowledge at that point are obsolete. It's a difficult time that not everyone can cope with effectively.