South Korea has been quietly preparing for the eventual collapse of the communist government in the north. South Korea has, for over a decade, been carefully examining the experience of Germany in reuniting its democratic and capitalist West with its communist and ramshackle East. As a result, South Korea has been developing an very strong civil affairs capability. Something like a half-million personnel (military and civilian, active, reserve, and retired) have been trained to assume administrative duties in the North in the event that unification takes places. Reportedly, half the civil servants in the ROK will move North as part of the reconstruction mission, and will stay there as long as it takes.
The South Koreans have been very quiet about this effort, although its no secret. But publicizing it would only antagonize the already erratic and excitable North Korean government. The South Koreans believe there is a high probability that the North Korean government will eventually collapse. If that happens, the South Koreans want to maintain order in the north, and avoid mass movement of starving and terrified North Koreans. Ideally, South Korea would like to see North Korea evolve into a democratic country with a more efficient market economy. But thats considered a long shot. More likely is a collapse of the government and economy up north, leaving South Korea to rush in with its military and civil affairs units to maintain order and provide needed services.
The South Koreans also have to prepare for a possible civil war in the north, which is another worst case situation. Its not known how much South Korea and China have been working together on peacekeeping in the north. It is known that China is very concerned about collapse in the north, and hordes of starving North Koreans pouring over the their border. China does not like the idea of a united, democratic, Korea. But China doesnt want a collapse in North Korea, and chaos, either. No one wants that, but North Koreas neighbors are preparing for the worst.