Think about it this way, how many people does it usually take to build a house? A dozen seems about right when I look at building sites. How many people will it take to assemble a printed house? 2 maybe 3 and in 1/20 of the time, that's far fewer hourly wages. I'm not sure new branches of work will appear this time.
And builders are quite skilled, some are very intelligent. Who would have need for a less-intelligent, semi-literate person who can't perform anything but very simple manual tasks well? These people do exist and no amount of training will make them more employable. Then what about later, what if A.I becomes so good that it's not economical to employ highly-skilled people like doctors or engineers either?
Yes, these days you don't need that many workers to build a house. This should move house prices down. Of course it's not happening due to unfair monetary policy where printed money is causing bubbles and majority of people can't afford buying a house.
New branches will appear. 20 years ago it was hard to imagine services like steemit, technologies like bitcoin etc. The fact is that we will be doing more work with our brains.
Advanced technology is a great chance for less skilled people. I will give you an example. We have these days AI technology that is better now in analyzing MRI images than humans. It means you can use software and analyze image on your own. Later you can use software that will give you diagnose. This is something that can be done by unskilled person. No doctor is required. The whole thing with automation is to do job once and simplify/reduce amount of work you repeat. In this example you train your neural network with medical data and diagnoses prepared by experts. It should move health care prices down, which is a good thing. Doctors will be more busy with research than with prescribing paracetamol.