Sure such a conflict would make lose a lot of people but if it is not avoided it is that a majority of peoples would have let it done.
This will probably never happen, and if it did, I am guess about a billion people would die and that Russia would be totally dismembered in the surrender. Also, China would be forced to cede Tibet, Xinjaing and Manchuria. Korea would be reunited as well. Perhaps the EU would expand to Moscow's ruins and become a united country.
That's exactly, in part, the result I would expect of such a conflict, except the last sentence. I think the possible future former Russian Federation would become a EU-like, and maybe the same thing for most of the current Chinese territory.
Well, as I often say: Maybe, maybe not, anyway for me these things are possibilities.