These are two separate problems. One is the increase in productivity; the second is the application of that productivity to creating new wealth and industry. You are worried about the second not happening; this is a result of capital concentration and income inequality, which stymies investment going where it is needed. But we can't seriously pretend we are running out of useful work for people to do. A half a moment's thought should convince us otherwise. We just need to be able to allocate capital to that work.