I fully expect China to take part of Russia possibly via Mongolia once the Us is marginalized and weakened.
One only has to look at geography and demographics to see the incredible lure that concept has for China.
145 million inhabitants in the largest country on earth vs 1.5 billion who need breathing room?
Also, Russia can’t afford to lose too many people because of war. China would probably shrug at the concept of losing a few million?
The only problem there is nukes. Would Russia be willing to use them to protect Siberia.
All of Siberia, which is huge, has only about 25M people and dropping.
Maybe, but China would be taking a big bet that Russia wouldn’t make that 500 million dead Chinese when Putin decides to use that aging Russian nuclear arsenal. A better deal would be for the two of them to come to some deal that benefits both of them such as Chinese funding in exchange for Russian space and gas.