Robots would do the work. The future may not need many human robot operators either. If the world only needs a couple hundred thousand people to run the robot

Robots would do the work. The future may not need many human robot operators either. If the world only needs a couple hundred thousand people to run the robots, maybe there will be enough of them who are willing to do it just because it is fun to run the robots and provide for the world. People do charity all the time today and the world of the future would need much less charity. Obviously most people would not be interested in doing this work for free. But fortunately we might only need. 0.001% of the population to be willing to do it for free. I expect that at least 0.001% of the population in the future will be charitable enough that they will be willing to do work for free in order to provide for the entire world, by running the robots.