It's an excellent opportunity for China to demonstrate the superiority of their system, as they so frequently claim.
We'll play a little game. Open immigration into China for US citizens. Open immigration into the US for Chinese citizens. Let's see who gets the most immigration (it'd be lopsided 1,000 to 1 with millions of immigrants flowing into the US; we did it with Cuba from ~1960-1980, there's no reason we can't do it for people wanting to flee China; if the next Democrat President is smart, they'll implement a variation of this to create a more aggressive and persistent brain drain on China).
https://www.reuters.com/article/us-china-germany-hongkong/ch...
My guess is, HK nationals with linked anti-state activities will likely be denied ability to leave the country. If relations between China and West get particularly acrimonious, this will include foreign HKer with foreign passports who reside in HK under their HK citizenship - i.e. they get treated as Chinese nationals foremost since they never renounced their HK/Chinese citizenship. Many HKers with goldenticket passports who thought they could protest (read: foreign influence on Chinese affairs) consequence free may be in for a surprise. The entire situation can get off the rails.
I think what China is most likely to do is Integrate HK into greater Bayarea, squeeze protesters into margins of society and out of HK by blacklisting them from local opportunities, disperse 4/7 million rebellious voices until it's drowned out by 66/70 million pro-CCP voices. Basically what Social Credit was designed to do: expel non-productive people or those that burden Chinese development out of privileged areas and visibility. Indoctrinate new generation to comport to CCP values, replaced displaced dissenters with mainlanders. HK becomes just another tamed Chinese city.