The entire family is in power, and to the best of my knowledge Un wasn't actually the first choice. I can't recall the name of the Kim who was, but I believe he was a premier who was ousted after a failed economic gambit (a currency or some such). I just don't see the regime as being that unstable. We, from the outside, often like to believe that people yearn for the yoke to be thrown off... but that's the type of thinking that had us believing that the Iraqis would welcome us as liberators. Sometimes shackles can be comfortable, both to those living with them, and to the rest of the world. We aren't seeing any coherent grassroots movements among the North Koreans like we have in the Middle East (and even that hasn't gone well), and the world's diplomats don't seem to be too concerned. The reigning theory from both those enduring, and the experts, seems to be: Better the devil you know.
Apathy isn't the same as a person having a sense of sheer helplessness and not acting because of that. I wonder how many North Koreans fit into those that are apathetic, those that are brainwashed into liking and following their leaders, and those like I said above just feel so helpless that it seems like they fit into one of the other two categories when they don't. I'd like to think that even after all the propaganda and brainwashing they have been subjected to there are still a lot of North Koreans that want things to change but feel too helpless and scared (for a very good reason) to show it.