If that happens and the regime falls ... what next? Anarchy, very likely direct military rule. And the country does have some nukes, however small; and they have plenty of permanent hostages just across the border.
Let's turn to recent history. Socialist rule ended in the USSR. Some republics, with deeper democratic roots and history, and with better educated population, immediately elected new parliaments, presidents, and went on as if nothing happened. But some other republics instead allowed *individuals* to seize power and use it to fulfill their personal ambitions - pretty much the whole group of Southern republics is in that category (and Chechnya, after Yeltsin removed all oversight there.) Many of these republics saw wars, poverty, tyranny.
I personally have no idea how to bring NK people to the light side of the Force. Many people were born under the dictatorship and never saw anything else. Foreign news are banned, so they hardly know what happens in the world. I'd say they are in very precarious position, set up for a major paradigm shift, if I may use those buzzwords. South Korea is on the opposite side of the scale, not necessarily a gentle Big Brother.
The regime in NK will definitely fall sooner or later. Even now attempts to install the son of Kim are causing grumble. It wasn't supposed to be a hereditary monarchy, but it is. I think the Army is aware of that, and will dump the Dear Leader and his son as soon as necessary. And the Army will not surrender its privileges unless all major decision makers are paid enough to just walk away and retire in better climate. That is an option.
That will give them some leverage to dictate the situation in N. Korea. For the rest of military (some one million,) they would rather not fight. They could bail out at the first opportunity they can find.
China would be also using them to get their say in Korean situation. We need to enlist help from ordinary people to flush them out. I think ordinary people have dim view of these creatures. Just like Romanians smoked out Securitate die-hards.
You left out China. In china the oldways are being carefully folded and put in cabinets. A very gradual transition to something not really known is in process.
North Korea is the hegemon of China. China will ease in and control what ever happens. IMHO