China has 250,000 men stationed in Dongbei so it'd be easy to invade at short notice (that's probably a big reason why those troops are there in the first place). Whatever happens Beijing isn't going to give up the strategic depth that North Korea provides. Also obvious however that the Chinese increasingly see NK as unsustainable on its current path and want Pyongyang to carry out Deng Xiaoping style reforms, hence the planned coup for Jong-Un to make way for his older brother.