An answer from a not-qualified source

I'm no scientist, and in attempt to be objective, I'm a pacifist afterall, thinking, or having faith in, the instictive guide of our natural selves, meaning; our bodies, will (and have already in places such as India, and several nations in Africa) act as mediators, inableing fertility, and leveling off.

And, by the looks of it, people keep being fertile, so I guess we'll just have to wait and see.