One possibility of what would happen if there were a war/conflict would be China would take over NK and create a buffer Chinese state, possibly another country in the Two System, One Country philosophy. China is becoming increasingly intolerant of DPRK's actions, as evident by their stopping importing of coal due to the killing of Kim Jong-nam (which will hurt DPRK's economy as it is a large part of their exports). My guess is that the buffer country would be a compromise, since SK doesn't want China directly at their door and vice versa, but SK wouldn't be able to really support NK's terrible economic situation as their economy is too small, and the US wouldn't want China's influence in the region to too much grow. I could see another part of that compromise would be to allow NK citizens to go to SK to be with family, be reeducated, etc, as well.