Here in the States, Korea is often referred to as the "Forgotten War". This is not because it is forgotten that it happened, but the American people have forgotten that we are still fighting it, although through diplomacy rather that militarily. American service members still receive war-zone pay for being stationed there. China will continue to support a regime that they may not care for, if for no other reason than to dilute the attention of the U.S. along a wider range of protagonists in the South Pacific region.
The Korean Conflict is actually a relic of the Cold War, morphing itself into a twenty-first century player of a dance begun at the Paris Conference of 1919. Both Japan and China walked out of that conference without any agreement with the European powers, or President Wilson, and the groundwork was laid for the decades of tragedies that mostly occurred after WWII. Even through the war, and especially after it finished, America's continued support of the government that became Taiwan, combined with it's protectionist treatment of Japan, led many Chinese Nationalists to believe that their very culture was an under-appreciated asset to the West. Nothing has been done in the last 60 years to change that, and the case can be made that there is a much greater sense of urgency by Western diplomats to change that perception. It may be too little, too late.
Even before this dubious campaign in Iraq, and before this necessary but futile prelude in Afghanistan, China was testing the prowess of America in the Pacific. (Remember the Chinese fighter who grounded an American spy-plane just after President Bush took office in 1990?) Even Russia is now looking to settle scores with Japan, which the U.S. has sworn to protect, with claims dating before their war of 1905. The point is: North Korea has never been more valuable to China, whether proxy or not, because it presents another threat that the U.S. has to be worried about. If anyone dies in South Korea, the U.S. will receive as much blame as the South Korean government. It has become a political liability that won't disappear, regardless of the tenor of the administration in Washington. My beloved country is too involved to quit, too broke to continue, and too distracted to decide.