If robots generate all of productivity and human labor is no longer needed, the economy would not be able to sustain itself. Instead, in trying to cope with the unneeded human labor and to ensure continued productivity, the only area where productivity would be ensured is by means of war using human resources, namely destroying things in order to be rebuild, thus generating a sustaining feedback loop. The rich will get richer and everyone else will only be employed as soldiers in a continuing war economy.
Even though this is a sci-fi concept, i believe it's not a stretch to say we are headed to this direction.
We're already there, in a sort of way. Products aren't built to last, aren't built to be repaired. Buy a new phone, computer, washing machine, every year! You wouldn't want the social embarrassment of not having the latest gadgets! And if that fails, we'll just release a patch that prevents the irreplaceable battery from lasting a full day.
Plus after computers made it so one person could do the job of 100, entire new industries popped up to do meaningless jobs shuffling digital money around. Some of the most comfortably-paying upper-working-class jobs are entirely pointless. But it keeps educated people from questioning the system. As long as they get a cushy paycheck twice a month they'll happily make another B2B web 3.0 cloud-based KPI tracking analytics platform and not question if their job is meaningful.
Well I mean Orwell hit on the same concept with 1985, with the major powers just rotating who was blowing up who at any given time in order to keep the proles in line.