Isn't that basically a good thing though? I'm not wishing for humanity to die out, I just think that the best way to minimise net human misery is to have a smaller population. If it's happening naturally then all the better.

As "native" developed country populations decline, I can see increasing tension as developing country populations continue to grow rapidly.

There's also the small problem that our accepted economic models seem to rely on perpetual growth.

Many populations are probably auto limiting themselves because we are walking the threshold of resource availability. Another kid means less food in your other kids' mouths and less chance of survival.