People asked the same thing when millions of farmhands were put out of work by the McCormick reaper and other pieces of agricultural machinery. People and markets adapted. They did not become idle and live on the dole, which would have been unthinkable.
Yeah, those people went into manufacturing. And then when manufacturing declined, they went into the service industry. But both manufacturing and services are being automated. What then? I hope you are correct, but its not clear that anything is left. My hunch is that we will have a lot of relatively educated people with not much to do. That is not a formula for social stability.