I suspect, without proof, that fertility will rebound to some degree whenever the general population feels financially and socially secure. There’s no need to have children, so it has to be an option that doesn’t seem inaccessible like it does today.

> ...whenever the general population feels financially and socially secure.

What if the enormous cultural and economic problems caused by (among other things) the incredibly top-heavy population pyramid prevent that from happening?

You are describing a temporary event.

You can’t out-negotiate biology, and it doesn’t take polls. People don’t consciously think ‘time to repopulate,’ they think "let's sleep together'.

Tonight is really as good a time as any to make a baby.