By the time CL makes any decision to close the border with China it will be too late, the ball is quickly rolling. Soon the only country that will still accept anyone or any flights from Hong Kong will be China itself.
Also, since lots of countries are now turning away or quarantining anyone who has been in China in the last 14 days, how does this affect crew either operating or passengering to these countries if they meet this restriction? Will a turn-around flight also count as having been to China?