Machines will need humans, for sure. The question is how many? For instance, there is a company using printing technology to build homes in Austin, Texas. The target number of workers needed to operate the "printer" is 3, down from 10. So on the positive side, the remaining 3 workers will have a better work environment, maybe the costs of building houses will go down a bit, etc. In the other hand, 7 workers are no longer needed. My point is that the gains in efficiency will come with some winners and, in my humble opinion, many losers. And that will only help to downsize the middle class even further. Don't get me wrong, from a scientific/technological point of view, I am looking forward it. But I am concerned with the social impact in the long term.