Opposed Systems Design

The Chinese Foreign Ministry said Tuesday that a North Korean border guard shot dead three Chinese citizens and wounded one last week in northeast China, prompting the Chinese government to file a formal complaint.
…It was unclear how the shootings would affect relations between North Korea and China, which is North Korea’s closest ally in the region.

With behavior like this, I wonder how long it will take China to get fed up with North Korea and decide that it wants to create a better option. China might wish to maintain the status quo but North Korea has been the one upsetting that status quo. If China can’t control the current North Korean regime, then will it play a more active role in shaping the next regime?