They might be enough to tip the scales. The west, as a collective, have already provided huge military aid, intelligence capability, and crushing sanctions to aid Ukraine, but that hasn't stopped the war. China is quite clearly not happy about the war in Ukraine, given their relatively neutral public standpoint about it.

China make up a larger portion than ever of Russian exports as they soak up excess resources that would previously have gone to Europe, as well as 2/3 of their imports, giving them a real ability to put pressure on Russia. I'm skeptical about what the quality of their peace plan will be like, but having them advocate for an acceptable peace would be a huge blow to Russia.