You are correct. I saw a report that 2,000 guards were sent to the NK border yesterday.
The Chinese are worried that if there is a leadership confusion, many NKs will make a run for the border.
Rumor has it that Kim Jong-un’s uncle, Jang Song Thaek, will rule behind the scenes.
That appears to be the case, yes. Tense border, but very quiet right now. Hordes of North Koreans in Chinese border towns being ordered to return back to North Korea. Many going with flowers and then across the bridge from Dandong, China to the other side. Pyongyang run restaurants closed down for a number of days, in mourning.
“Rumor has it that Kim Jong-un’s uncle, Jang Song Thaek, will rule behind the scenes.”
Reuters is confirming:
http://in.reuters.com/article/2011/12/21/korea-north-army-idINDEE7BK05H20111221
“Jang Song-thaek, 65, brother-in-law of Kim Jong-il and the younger Kim’s uncle, is seen as the power behind the throne along with his wife Kim Kyong-hui, Kim Jong-il’s sister. So too is Ri Yong-ho, the rising star of the North’s military and currently its seniormost general.”