People became more productive due to technology. Now you are able to produce enough for you and your family in 40 hours / week. Before this technology advancement, you needed to work 60-80 hours / week in order to produce enough.
People didn't need to work 80 hours a week to produce enough for themselves, they needed to work 80 hours a week since the means of production were controlled by greedy assholes who only gave bare subsistence wages to the people who actually used them. And they still are, even if the labour unions and the threat of communist revolution helped curb the worst abuses of the robber barons of the Industrial Revolution.
What will happen if we are super productive as that professor claims? Have you seen the Jetsons? that is pretty much what will happen: you would work 2 days a week for 5 hours / day.
That'll only happen if you're your own boss. If you work for someone else, why would they have you work for 10 hours per week when they can keep you working 40-80 hours and pocket the increased profits?
Your job would not be canning tuna, but making sure that the machine that does it gets maintenance.
Nope, that's automated. It already should be.
We would spend our time, doing art, music, entertainment, or any other leisure related activity/job.
This would be the best outcome, and it'll eventually come to that; the question is, how painful will the transition from our current model to that be?
Consider this: we don't have to work to get air.
Nitpick: you are, in fact, doing work right now (or at least I sincerely hope you are) to get air. It's why you have muscles for it.
Jobs are not a scarce resource, labor is. There is always enough jobs for everyone that wants one and then some, even if it means being self employed. The only reason there is unemployment at all, is because of bad laws.
Unfortunately, this is not true. Being self employed means that you have to find a demand you have a skill to fulfil. Such demands might exist in quantities sufficient to employ everyone, either in actuality or in potential, but that does not mean that all unemployed people will find one.