They currently have no political trade advantadge, they need to make sure USA has a good reason to accept their trade offers. North Korea is totally isolated and this is always very bad for business. There is also the fact Jong-Un must stablish himself internally and he is using the hate 'his' population has towards South Korea to gain immense popularity (mostly internally in the army, which is the main force and institution in NK). This will sound very weird, but since the World is not into going to war nowadays (the economic crysis is too big atm to let it), this may very well work on North Korea's way... EDIT: I dont feel that much dangerous in these bullshits, but they must cool things down a bit. Making threats every day isnt very smart, give it sometime in between, lol. The possibility is huge for a NK vs SK naval battle on their small islands (which is bad enough). EDIT 2: I just dont believe it will be more than that...