The Economist predicted this last year saying that the transition period will be fraught with intense internal division unless Kim Jong Il stepped down and transitioned power himself before he died. He didn't.
So what you have is one son (of many) trying to corral a vast military establishment. Meanwhile China, the only official sponsor of NK, wants to see stability in the region above all else. Their ambitions in the South China sea are paramount in handling this situation.
Consider this essential reading:
http://www.economist.com/node/21542227