I don't see this plateauing theory as a cause for hope. So we get to 10 or 11 billion and then level out? What's to celebrate in that? It's heIlish already at 8 billion. IMO 2 billion is the absolute maximum number of human beings this planet can sustain.
I loathe the way this subject is always discussed from the perspective of what industrial human societies desire and what they think they can get away with, as though that's the only parameter. "There's still room for more yet. We can shove a few more in here, build another megalopolis over there. We'll eat insects, build wind turbines, desalinate the oceans, irrigate the deserts, mine the moon. We'll live in urban termite mounds communicating feverishly [and pointlessly] through screens about nothing". Really...?
The vanity and self-centredness of it all turns my stomach. What about other forms of life FFS? What about wilderness? It isn't "empty" or unused. It's busier and employed to better purpose than anything we've created. We have no moral right to claim dominion over this planet. It isn't there for our convenience. We have non right to colonise it, monopolise it and strip it bare and turn it all of it exclusively to our purpose, and then celebrate the ruin we've wrought as though it were some sort of perverted evolutionary achievement. There is not a human being ever born who was worth any more than a single blade of grass.
I'm out of this thread now. It makes me too angry an too despairing.