It will be a challenge of the century to see if socialism can fix this crisis where capitalism clearly hasn't.
I certainly hope that, as China improves living, working, and social conditions, that birth rates rise back up to replacement rates or higher. That would cement the superiority of socialism and prepare the world for the population required to expand into space across the solar system.
Eh, it's a matter of investment into the technologies required for bulk space transport. Infrastructure like space railguns (basically a really long Hyperloop section that points towards the sky to shoot payloads into space) are feasible today (and China is researching them already: https://newatlas.com/space/china-railgun-spacecraft-orbit/ ), and more out-there ideas like space elevators are a matter of time. In order to reach full communism without strip mining the entire Earth, getting resources from lifeless space is essential. That will require lots of people in space.
The interesting thing to see at this time is if China can show another way to sustainable population management. Capitalist countries seem intent on shrinking their overworked populations into nothingness. South Korea's birth rates have only decreased further, even as their population keeps shrinking.