China invasion is a popular scarecrow in Russia, but it will not happen. Thinking anyone is envy of big Russian territories boosts the Russian self-esteem, but it is a lie. Rarely anyone thinks what will China actually do after it had sucessfully invaded Siberia.
The Siberian lands are hostile. Both Tsarist Russia and USSR managed to set up cities there only by propaganda and forced relocation. It's better to set up a puppet government and suck out all resources than to actually invade a country. Which is what is happening right now.
The only thing that might happen is that some China leaders will try to gain a small territory in order to earn political points at home. But that can happen only after Taiwan has been be conquered, which is still a big problem for them.
The future of Siberia is grim, it will probably continue to collapse into a No man's land, scarcely populated territory without any laws, ruled by local mafia leaders. Something like Libya is today. And no one will really care about it, other than buying oil from whoever sells it. Again, like Libya.