The question is whether the segment of people who used to fill these jobs can be channeled towards other types of jobs or if we are facing a future where a large portion of people will have to be supported indefinitely because there won't be any place for them in the workworce.
In effect, we are doing that now with extending unemployment and other forms of government payments.
If we keep going the way we have been for the past several decades, your question will be valid. But -- and this is also a response to the "close the borders" crowd -- if we remove the heavy taxes, unproductive regulations and the government-caused shrinking dollar; we will find that the economy will spring back to life.
People have been worrying about the effects of free trade and automation for centuries, and it's wrong to think that it's somehow different this time. Man must work to survive and he will. If government only lets him.
Note that “minimum wage” means it is illegal to pay workers what some jobs are worth, and other regulations make it hard to hire. Given the need to do the job, and the encroaching prohibitions and restrictions on having humans do them, machines fill the gap.
I’d rather a human wash my dishes and sweep my floors, but a few hundred bucks for a dishwasher and Roomba are just so much easier than the gov’t paperwork & restrictions.