Frankly, I think this is a real cause for concern.
There are several ways of preventing a situation where there are too many unemployed or underemployed humans, but I think the most effective would be population control. Population control, kind of like what China has done. China is one of the fastest growing countries technologically speaking and yet is the most populated country in the world. They have somehow managed to control their population over the years, built and sustain a strong economy while trying to maintain optimal employment of their human resources.
If there is to be a world where robots would be used in place of humans for jobs, then the world could learn a few things from what China has done.
China did not “somehow” control their population. They made laws limiting the citizens to one child. Being a Government they did not see their own folly (the law of unintended consequences). The couples who would now have to rely on only one child to provide for them in old age, tended to abort female children. China now suffers from a lack of marriage age women.