The only way North Korea's regime will be overthrown is if these same Chinese people overthrow theirs first. Then NK's biggest enabler will be out of the way and their will be little to stop its collapse.
Russia won't allow it.
I've heard Russia and China are teaming up to explore potential offshore oil reserves off the NK waters.
If they find any, you bet your ass they will do everything possible to keep Kim in power and exploit it for all its worth.