Kimba is right. of course: officially, there is only a truce, the Korean War never actually ended.
Eventually, Korea will be united, but of course, because the North is a poor Third-World country and its people entirely ignorant of the way life in a modern capitalist society works, they would be lowly peons in the new, united Korea. The South is clearly a first-world industrial country, the Northerners would be a supply of not necessarily useful manual labor. So far, the main contribution of North Korea to the World economy is the sale of the human hair of its women, which is sold in bulk to the South, then packaged and marketed by Koreans in Korea and all around the world. No flea market in America does not have dozens of Koreans selling hair to Black women and others.
The leaders of North Korea, not just Kim and his clan, realize that there will be no place for them in the new united Korea. They are entirely unprepared to be united Koreans. At least East Germany had industry, but many of the Osties of the old DDR were impoverished and confused drifters for many years. This is not to say that eventually, all Koreans would benefit from unification. But it will be a process that will take at least twenty years. If one is an old fart in the North Korean politburo, that is beyond their expected lifespan.
The sinking of the South Korean boat was a message that, in the absence of th4e "Sunshine Policy" of the previous Korean government, the North was not going to allow itself to be pushed around.