This is what I am thinking too. I think that meeting with Trump has got China thinking it needs to reign in North Korea.
The question is, “What’s in it for China?”
China probably would demand, in exchange to allowing the North Korean regime to meet its’ end, for US troops to leave the Korean Peninsula when the North Korean problem is resolved.
China and South Korea aren’t exactly enemies anymore, although sometimes there are tensions between the two.
If the US did not have multiple plans for dealing with the Norks- that would be news. Hopefully the US and China came to a mutual agreement that Fatboy and his nuclear ventures must come to an end. What happens afterward is the tricky part. Chemical artillery rounds fired into Seoul would not be good and probably hard to stop. Interception of bigger rockets would hopefully be reasonably easy. Best option-China induces the Nork military to eliminate Fatboy and then start the process of elimination of all nuclear and chemical weapons along with stopping the support for other nuke wannabes and terror regimes. International help would be forthcoming for the Norks and they could become a more open society joining the civilized world.