it's a bit hard what to make of this, as most of the vague rhetoric in the press indicates. you can't invade them, for lots of reasons but primarily because they line the border with missiles constantly pointed at Seoul and have said that regardless of who is doing the invading they would respond by flattening it. but beyond that no one really knows very much about what goes on there.
the out pouring of sympathy is probably a mixture of genuine grief, public show in case too muted a response will warrant punishment and just general worry about where the country is going. but to what degrees no one can be sure.
I do worry that some leaders are going to try an exert a lot of pressure on his son, who is probably too young to really handle everything and may not have the connections with in the upper echelons to control everything and could well act eratically if pushed too far.
there is no real pattern to these things. when franco died in spain it was a day later that the country begain to move towards democracy, whereas lenin handed over to stalin who was a much fiercer despot.