The last SF team I was on had a heavy focus on the Korean Peninsula and we were involved at very high levels with the Korean military leadership and the Special Ops plan for response to a North Korean attack. It was amazingly daunting on the surface as the North has amazing numbers of men and materiel. They have huge tunnels full of tanks and APCs right up by and sometimes in the DMZ ready to roll South crushing resistance under it's massive juggernaut. They have hundreds of artillery pieces in hardened bunkers that have Seoul itself in range. They can launch wave upon wave of infantry to swarm any resistance long before we can get reinforcements to oppose them. We're doomed Christopher Robin.
Except they really can't. Even in the 90's we didn't believe that the numbers bandied about were legit and mission capable. The North has always siphoned resources and starved its civilian populace to support the military, but even so they just don't have what it takes to mount an all out assault. By now the bulk of their equipment has not been maintained and is rusted and useless. They don't have the gas and oil it would take to roll any significant armor formations and their ammo supplies would be exhausted quickly. They simply cannot invade the South and win. So they won't. What they can do is conduct an irregular/asymmetric campaign and if they chose to that could be a tremendous problem, but I don't believe they will.
First let's look at why they are acting up now. There is a succession struggle playing out as Kim tries to position his son as the next Dear Leader. There is considerable opposition to this even in a society as tightly controlled as the North. Kim moved some people loyal to him into positions of authority in the military to solidify his power base, but he needs crisis and the ability to negotiate for the staples they so desperately need. Thus the sinking of the South Korean ship and the rest of the saber rattling. The modus operandi of the North has long been to create a crisis so they can rally the people against outside forces threatening their sovereignty. Then to use that to extort money, oil and food since they are always chronically and often critically short of those. Add in the ability to land his son the gig as next in the cult of personality and you have pretty much explained the current spat.
If they are actually looking for a larger scrap as I said I don't believe it would come in a mass attack, but rather in sabotage, and low level infiltration. The North has large numbers of commando teams and they could wreak quite a bit of havoc without the huge provocation of rolling tanks. Even so, I don't think this is anything more than another shakedown and succession drama and it is likely that soon we, the South and the Chinese will be shipping some food and gas their way to calm things down.