China has lucrative trade with South Korea. The Norks are a drain on China and IMHO Beijing would like to see an end to it. China has no fear of SK, none at all. They can buy up the whole place if they want to.
Also, Nork refugees pose a SIGNIFICANT threat to the border region. Refugees would pour across that border in numbers even China couldn't handle.
That's bad for business.
No, China no longer needs the Norks. They have become a stone around Beijing's neck, and its time for them to go.
This is how China sees Korea, and they now like the south more than the north. Count on it.
Exactly. Add to that that China forty years ago was very similar to North Korea - today they are very similar to South Korea, if not more advanced in some ways. They have moved on to a big corporate role and left their ugly little brother behind in the Communist orphanage. :)