Bummer, but not unexpected.
I wonder if and when this will affect Xiamen Airlines. They’re 55% owned by CZ, so you kind of expect they will follow the mothership, but they may wait to make the move for another year or two until CZ’s new alliance membership is solidified (almost certainly in OneWorld).
This leaves SkyTeam with a gaping hole in South China you can fly an A380 through, although I do agree CZ/MF weren’t really filling that hole well given the limited nature of the partnership. I wonder if HX would be interested in an alliance?