It is believed that China will attempt to gain control of some disputed islands by military means, possibly even Taiwan, as a way to show the Chinese public that its leadership is competent.
They can only do this if the United States is not involved. If North Korea can divert US military attention away from Chinese military action, then the Chinese can take these islands easily, and (as the theory goes) stabilize confidence in Chinese communist leadership.
Expect North Korea to make a minor push into South Korea, or set off a nuke on/near a minor US holding. Something that will require full American attention without causing a full-blown war.
And yes, a weak and inexperienced American CIC with communist sympathies, is part of the Chinese-NK strategy.
Meanwhile, Soetoro and his wookie wife are busy planning the White House sequester concert..
I think you are on the right track... but fail to see the bigger prize ...
China could use this as an excuse to take all of Korea.