Unknown. It's never been tried in an industrialized nation. I have a feeling it could easily go the other way and return China to poverty with not enough people to sustain their current economic output. That depends a lot on what's possible to do with automation. It could also have drastic effects on the knowledge sector, breaking down chains of training and knowledge transfer. A lot of expertise could be lost.

probably the opposite.

In the black plague, most of the wealth was durable physical assets like land, tools, farmhouses, ect.

In modern economies, wealth usually buys services and consumables. Less cheap labor will be a big hit to these costs. To make things worse, the workers will have to financially support a large aging population with a shrinking young demographic.

It depends on how you measure it and how it happens, but if each couple has one kid, and that kid inherits from both parents, after awhile the kids are inheriting a decent amount.

Or, all the excess "wealth" could be sucked up by the government/companies/large land-holders and everyone else stay roughly the same.

The End of The World Is Just The Beginning delves pretty deep into this. Very interesting read.

Don’t think so. This isn’t a case of population declining because of a one off event, killing off the old and infirm first and leaving behind a (relatively) healthier population.

This is more of a gradual decline AND ageing. The decline isn’t happening because the old are going away; its happening because there are too few young people being born.

That just leads to stasis. Nothing wrong with that, but it completely messes with all our current economic and governance models