This is all in China’s hands. Kim is screwing things up hugely in DPRK, but China does not want instability, and particularly does not want any opportunity where Japan, S. Korea or USA can have future influence in that country. China’s goal is to maintain a friendly, pliant buffer state on their border.
Most likely scenario is China initiates some kind of quiet coup or purge of the Kims - and allow some good, old-fashioned Communist apparatchiks to take over, who slowly introduce economic reforms while keeping complete control over politics (Deng Xiao-ping theory!)
The ensuing Korean nationalism and unification question will need to be dealt with, but only slowly.
The result is extended uncertainty in which China and S. Korea/U.S. are each trying their plan while neither of them could get decisive upper hand. Besides, N. Koreans themselves are wild cards. Nobody can control to the satisfactory degree how they will react, especially when none of the outsiders have a free hand to control the situation.
Things would be pretty fluid, and would create many surprises.