Well one, getting to post-labor has nothing to do with raw population figures. No matter how many people you have, they want to eat, probably want comfortable living (housing + climate control), and in a modern context want Internet access and electricity.
You could have a hundred billion people and everyone would still want that. The difference is post-labor comes when you don't need human capital (or at the worst, a negligible amount) to produce the necessities for people to survive. We are approaching that, look at how manufacturing is returning to the US in 99% automated facilities. Once you can grow food (or fabricate it with molecular engineering) without requiring human labor to produce it, you can already distribute it with automated vehicles, and you can produce electricity via solar, hydro, or nuclear wtih very little human capital involvement after you set the system up.
The idea is you put systems in place that the fruits of them are effectively infinite without human engagement. Once you can do that, you have post-scarcity bounded on the limits of the planet and our ability to deploy infrastructure, not in how much labor we can produce. We are getting there, but the fundamental problem is we try to squeeze these no labor return systems into classic market capitalism and it isn't working (a concentrated wealthy class ends up owning these means of production, and power and wealth are concentrated as a result).
You could have a hundred billion people and everyone would still want that. The difference is post-labor comes when you don't need human capital (or at the worst, a negligible amount) to produce the necessities for people to survive. We are approaching that, look at how manufacturing is returning to the US in 99% automated facilities. Once you can grow food (or fabricate it with molecular engineering) without requiring human labor to produce it, you can already distribute it with automated vehicles, and you can produce electricity via solar, hydro, or nuclear wtih very little human capital involvement after you set the system up.
The idea is you put systems in place that the fruits of them are effectively infinite without human engagement. Once you can do that, you have post-scarcity bounded on the limits of the planet and our ability to deploy infrastructure, not in how much labor we can produce. We are getting there, but the fundamental problem is we try to squeeze these no labor return systems into classic market capitalism and it isn't working (a concentrated wealthy class ends up owning these means of production, and power and wealth are concentrated as a result).