Because its regime is one of the most loathsome in the world, there is a temptation to see every political development in North Korea as a precursor to the sort of instability that might one day lead to real change. So it has been with the announcement that Kim Jong Un, thought to be 27, a son of North Korean leader Kim Jong Il, had been promoted to general--a sign that he is likely to inherit his father's, and grandfather's, mantle. But the younger Kim is untested, the army has its own agenda, and China would like its ally to at least make some moves toward economic reform. So might the ice be about to crack? Don't bet on it. Loathsome regimes are not necessarily short-lived. The Stalinist hereditary monarchy in Pyongyang has lasted 62 years so far. (The Soviet Union managed 73.) It would be nice if the North's nuclear-armed government really were unstable, less because the world could then breathe easier, more because North Koreans could then breathe freer. But Kim Jong Un's ascension does not make so devoutly wished a consummation any more likely than it ever was.