Can you find me such an expert?
Certainly! You can become such an expert yourself in FIVE MINUTES just by reading this webpage. That will give you 4 minutes and 55 seconds more expertise than most of the armchair economists on Slashdot. It will even make you smarter than Stephen Hawking (at least on the topic of economics, but maybe not on quantum physics).
I'd very much like to understand what kind of gainful employment the blue-collar workers of today and white-collar workers of tomorrow can look forward to
Did you read the webpage? If so, then you already know the answer.
But somehow I expect that you did NOT read it, so here is the answer: Imagine a world where the robots exist that can do ANY job currently done by humans. Furthermore, imagine that they are faster by a factor of ten, than any human, at every job. So they can make an apple pie ten times faster than humans. They can weave baskets ten times faster, etc.
Now imagine two workers, Abby the Apple Pie Maker, and Betty the Basket Maker. Before the robots came along, Abby made a pie everyday, and Betty made a basket everyday, and then they traded a pie for a basket. But now, with the robots, pies are only worth a tenth as much, and baskets are only worth a tenth as much, so obviously, Abby and Betty will both starve. Right?
But WAIT A SECOND, while the pies and baskets have each fallen in value by a factor of ten, a pie is still worth ONE basket. So Abby and Betty can just continue life as before. The robots changed nothing.
Of course this is a simplistic model, and real life is more complicated. In real life, the robots are going to be MUCH better at automating some tasks than others. But this makes things better. If the robot can make 10 pies in a day, but only 2 baskets, then a basket is worth 5 pies, and Abby can just switch to making baskets, and she and Betty will both be much better off. This is known as "Comparative Advantage". It is a basic concept taught in economics 101.
So as the robots take over more and more jobs, people will switch to the jobs that the robots are not necessarily bad at, but just less efficient at, and then trade the goods and services they produce for the goods and services that the robots produce. If you say "What if the robots are better at EVERYTHING?" then you should go back and read the webpage again, because you completely missed the point.
Now for the bad news: As robots take over, and more and more jobs are automated, we will almost certainly be better off. But there will be some "losers", and those losers will likely be the same sort of people that are currently losing: poorly educated unskilled workers in 1st world countries. These people are basically trying to compete with a servo motor, and and the motors are winning. We are not going to stop all technological progress because of these people (although we may slow it down for foolish political reasons), so what is the answer? We could try retraining them, but they already got 13 years of free education and failed to learn anything useful, so that is not hopeful. So the most likely scenario is to put them on some sort of welfare until we can get riot control robots perfected.