The fact Russia hasn't won in dominating fashion literally years ago is all one needs to know. Russia SHOULD have ed Ukraine up. Instead, they'll be lucky to hold onto their fake break-away republics.
Russia is a has-been, and China isn't even on Russia's level. In 50 years, China's demographics will be in the midst of hard tanking and their economy is already in shambles. The CCP will be doing anything to hold on to their power at that point.
There's never been a more dominant period for the USA, in all honesty. There's no way either country -- alone -- can challenge us outside of outright nuclear war. The only real fear now is if the two band together, and that would be even worse for China (sanctions).