If Russia goes at war with the US, I believe China would hardly remain neutral to them and allies. They wouldn't necessarily use military force, but today's already difficult economic relations would be damaged even further.
Why would China be involved in this at all? This war disrupts Chinese non-military takeover of Silk Road territories, where they are dominant economical force already.
The only losers in this play are Russians, where only "brightest" of them think of such crazy scenario, that you are proposing. People in a way do not differ from lemmings - even millions of them can be wrong on their way down from cliff. But, while they are running amok, they have a goal - for that moment.