[cydonian_monk]

I'm not so sure. I agree we will eventually reach a point where the global birth rate (and later population) goes down, but I don't think we're close to it yet. I suspect we'll hit 8 or 9 Billion before we start to shrink back again.

And if we continue to extend the average age, then we may never shrink in numbers (barring a major catastrophe or mass-migration).

[zerostar07]

Interestingly that's what more or less the UN predicts, too [1]. My milestone may take a few hundred years it seems

[1] http://en.wikipedia.org/wiki/World_population