It seems to me that the Chinese government has determined that they will neither yield to any of the demands nor crackdown violently. That means the protest can keep going on, but nothing substantial will happen. So it will eventually die down after a while - just my 2 cents.
We have learned from Occupy Central that those moderates are weak and self-centered. They can be wore down and waited out. The main issue is it doesn't take much for the moderates to come out to protests, and that embolden the radicals to think that they can continue the riots.
For the radicals, some estimates put their numbers between 20,000 to 40,000. The new HK police chief is a hardliner. For the past few weeks including PolyU incident, the HK police has successfully arrested thousands of rioters(radicals). This morning the HKPF has dispatched thousands of police to MTR subway and major intersections to deter and arrest any instigators. So if the HKPF can remain active in arresting these rioters and make no major mistakes, then things would eventually quiet down. But that is being optimistic.
If foreign entities or Taiwan continued to pour in more resources, then things might not die down or can even be escalated. If they pulled off something like Ukraine, then hell would break loose. The arrest from yesterday shows that they intend to frame the HKPF by using a Glock(And bullet proof vest and other standard police weapon) which is a standard gun used by the HK riot police. More importantly, the HK legislative elections would be held in September 2020. It is a must win for the pan-Dems camp in order to partially control legislative council and influence the outcome of selecting the HK Chief Executive in 2022. For the pan-Dems camp, they are not going to sit around and letting the riots to die down. If I am being pessimistic, then things would not die down and instead it would escalate before the HK legislative election.
There are two factors that are not good for the HK government. First, the support of the pan-Dems camp remains strong even after so much violence. Not only that, the pan-Dems camp has actively coordinated with radicals without consequences. That means pan-Dems camp has no reason to cut ties with the radicals. Second, it wouldn't take long for fresh recruitment to fill the rank for the radicals and new recruits would be even more radicalized. Can the HKPF fend off the future generation of the radicals that are more aggressive and brutal without bloodshed? I am not even talking about the HK economy or the long term fix. Things don't look good for HK.