So productivity as measured today is only going to decrease by the amount corresponding to corporate profits? How do you figure? What is that amount - do you have an estimate?

As the other reply points out, profits are probably not what you care about anyway, because profits often just become the savings of ordinary people. So you want the proportion of profits that go to the already wealthy, plus the salaries of the mega wealthy.

But regardless, that figure is some finite number and you're saying it's more than the productivity we're going to lose due to an ageing population: how do you know? Actual estimates for how much we could free up by getting rid of profits and CEOs are highly uncertain and often negative.