^I don't live in Seoul now, I'm living in China. My level expertise in this is based on my watching North Korean news blurbs for a long time, knowing North Korean defectors in South Korea, and the like.
North Korea actually locked down Kaesong in 2009, and that time they didn't even let the Southerners leave the complex when they did, they were stuck there for several days. This time, they let them leave, but they aren't letting them back in. So, last time, they had basically hostages for several days that they could possibly barter for aid over. This time, they have a bunch of factories that South Korean companies could scrap in favor of development in rural areas south of Seoul. Some of the factories have North Korean workers, but still, it's a smaller scale deployment than was projected when the Kaesong Industrial Complex was approved between the two Koreas, so there isn't much that the North stands to gain by keeping them open.
You have the lines of communication completely severed between the two, including the emergency military hotline, you have the Chinese military moving into place in Dandong and Shenyang, you have reactors restarting. North Korea's preparing something big, and they're trying to keep everybody's noses out of their business. Surely they aren't oblivious to the fact that America can track them via satellite imaging, but they're trying to get as many people out of their hair as possible so they can mount whatever they want.
On the flip side, the AP branch is still open in Pyongyang, they haven't thrown out people in the embassies in Pyongyang yet. If you start hearing that the British and Swedish embassies are KO'd in NK, then I'd be really worried. Note that the Swedish embassy is the only embassy that can give consular service to Americans in North Korea.
But at this point, what are they going to do? They have missiles trained on Seoul, but if one even launches, but fails to hit, the US and SK will invade, China or not. China MAY not be lined up for defense, but to bolster border security in the event of a refugee crisis worse than they already face coming across the border. They do have enough nuclear material to make 4 crude bombs, but they don't have anything to deliver such a payload to South Korea, they can't make the material small enough yet to fit as a warhead in a missile. Even if they had a reliable bomber plane, they don't have the fuel to even make such a delivery. If we even saw such a plane on our radar, they'd be dead before they crossed the DMZ.
So what this amounts to, in my opinion, is posturing. I guess like a RTS, if you're planning something big, you make sure any scouts are out of your area so there's no possible espionage, then you prepare it, then you launch it so that the enemy doesn't know it's coming. It's either that, or they're playing the "spoiled kid in the cereal aisle" role again to get what they want, which is food and money. I'd say 30/70 on that.
