What will China's future population decline do to world wide inflation?

I think the odds of this actually happening are probably and hopefully fairly low, but if China's ruling class believes that they're facing a doomsday scenario demographically for their own power, there's some level of crazy rationality to them forcefully using their population surplus advantage while it still exists.

Depends on whether we build machine capital fast enough to compensate for the fewer hands required to make things.

All in all everything gets way more expensive or stops being made because you need certain economies of scale to make it worth the time to build something that would otherwise be completely unaffordable if you reduce demand by 50%.