Well they are on track to have 50% of their population disappear in the next 40 years and a lot of economic upsets because of it. The fact they are isolated does protect against that, but presents other complications.

That’s what I meant by “trend”. 40 years is a long time and recently, fertility rates have frequently changed on shorter timescales.

Indeed, fertility rates can change rapidly. However it's foolish to simply claim it can change so it will. If the current trend continues the Japanese people and culture will be lost to time.

>A trend does not equal actually dying out.

Do you have evidence of a < 2.0 fertility rate reversing itself in human cultures?

I don’t.

But it wasn’t too long ago that people were afraid of exponential population growth leading to wars and suffering and the end of civilization.

Now the global population has started to stabilize and concerns have shifted toward shrinking populations in developed countries. I don’t pretend to know how things will end up, but it’s not a stretch to imagine scenarios where the populations in developed countries could stop shrinking and stabilize.