Falling birthrates

Japan population shrinks by one million census confirms

Given the chance by medical science and religious, political, and moral culture, people choose not to be parents at all or to have small families.

Populations stagnate or actually shrink, in either case creating distorted age profiles as the elderly account for an ever greater fraction of the whole population.

Economically, in the long run, Zero Population Growth or close approaches to it in the wealthier countries will force everyone there to accept a later retirement age.

Or it would, but humanity will simultaneously be faced with a revolution in robotics that will increasingly make redundant even the young, the healthy, the sharpest, and the most up to the minute.

So then what?