I think so, too.
China was willing to get involved in the 50's because for a century (some could argue > a millenia) China was constantly at war with something, most often a civil war.
China in 2010 has not fought a major conflict in over 50 years. Their soldiers have no combat experience. The lessons learned were lessons learned 5 decades ago.
I believe China's capacity to make war is effected by it's general lack of experience, and it would be unwilling to enter as major of a conflict as Korea would prove to be, with it's involvement.
It would be directly engaging what is still undeniably the greatest military power in the world without question - the United States. Without that, even the ROK is no joke in terms of military equipment and preparedness. Even without those two, China is endangering the odds that all of our debt to her will ever get paid back, and a potential boycott of Chinese products by America would likely collapse their economy.