I don't agree with the unspoken premise that China is a Svengali that can pull Russian strings to make them go to war. Russia is in no state to further invade Europe, and won't be for quite some time.
If China wants its two-front war, the time to move is now, but I don't believe they're quite ready -- especially since they're contemplating a 100-mile amphibious operation. In fact, the other day I read
an opinion piece arguing that it might be more likely that China would move to retake territory it lost to Russia in the 19th century. I'm not so sure of that, either.