I would argue that we are, as a planetary civilization, almost past the point where a war of that sort is even possible.
On the other hand, if China were to ever shun NK, I would bet that their government would likely collapse in less than a decade.
Sadly, China has a ton of reasons to want to prevent that, one of the bigger ones being the border with NK where many, many refugees would try to cross into China.
I could however see, someday, China agreeing to a massive backroom deal on a scale that would be unprecedented:
China abruptly works to ensure a complete collapse of the NK government, without any NK nuclear weapons either coming into play or any NK nuclear weapons going missing (except to China itself, if it wants them).
And SK along with a good chunk of the Western world agrees to immediately conduct one of the largest humanitarian missions in history, to ensure that nobody is fleeing NK into China unless they have tons of assets and they want to avoid repercussions for their actions.
There are, sadly, a lot of reasons why China wouldn't want the western powers capable of pulling that off to have control of territory that close to China though.
SK would be their safest bet, but SK doesn't have the resources to pull of that kind of a humanitarian effort.
And the chances that someone like the US wouldn't take the chance to plop a military base in what is currently NK seems awfully slim.