The next time N. Korea sinks a S. Korean ship, this war might get started. Even though the U.S. might get involved, I think such a war would remain conservative so as not to draw China into it.
I heard Robert Gates today on the subject, and in response to a question about our military forces being spread thin, he said that in a war with NK, we would mostly fight with the Air Force and Navy, and those have not been affected that much by our two wars.
In a forum called defencetalk.com, I quickly read through a debate of who would win a war between North and South Korea. It's not great, but it has its good points. This is a quote from Firehorse in post #83.
http://www.defencetalk.com/forums/army-security-forces/north-korea-vs-south-korea-749/