It's "fringe" because it's part of China, and even all 7+ million people in HK comprise less than 1% of China. I know many Chinese people, and they do not give a shit about HK's ideas about its own independence. They consider it China, full stop. The example about Seattle "declaring independence" the GP gave is actually quite apt. There is only one way this will play out.
I happen to vehemently disagree with what the PRC is doing, for what it's worth. But reality is reality and this script is going to unfold exactly as everyone thinks it will. In 10 years time I doubt there'll even be a border. Who's going to stop them? Boris Johnson?
