Have you given any serious thought to that question? I have not. Evidently neither has the US or South Korea. Read on at Banyan’s notebook:
(…) Even without invading others as Japan did, the North Korean regime will crumble, perhaps soon after the immortal Mr Kim’s number is up or possibly even before: reports of popular protests sparked by a hugely ill-judged currency confiscation may be a harbinger. Thoughts ought to be turning to North Korea after Mr Kim.
Yet as Sung-Yoon Lee points out in Foreign Policy here (the picture desk has a sense of humour), precious little thinking about it has been done by the United States or North Korea’s neighbours. At best, contingency plans exist for dealing with the short-term emergency generated by a collapse of power in Pyongyang. Even Chinese policymakers accept that American special forces might, or even should, move in rapidly to secure nuclear, biological and chemical stockpiles from rogue groups within the military. Chinese troops, in turn, would probably move across North Korea’s northern land borders to enforce the peace there. The Japanese navy would bring in supplies to the coast and pick up refugees in leaky boats. A massive humanitarian effort, led by the South Korean military, would get under way.