This apocalyptic scenario:
1) We develop no long-term immunity, no vaccines, perhaps because the mutation rate is too high.
2) The disease causes permanent lung damage, making each successive infection worse for the patient.
3) No antivirals get developed, or at least not ones which can be produced in extremely large quantities.
is perhaps the most important consideration right now, and I'm not sure how much discussion there is about it. The probability of it seems hard to estimate, but it should nevertheless be attempted, because the stakes are so high.
Covid seems to leave permanent lung damage even in young people. Let's say you are 30, get the disease now and recover. Say the vaccine does not get developed, the disease stays with us and you get it again in a few years. Now it's going it be worse. It still may not kill you. Let's say that no effective antivirals get developed which can help you. In a few years you get it again, and this straw breaks the camel's back, now you're dead.
The virus apparently has a mutation rate which is on the high end, unexpectedly large rate of mutation. This makes the vaccine less probable. How much less? No idea.
Some say that antivirals "look promising" but what does that actually mean? No idea. What are they going to cost? What is the theoretical maximum which could be produced on this planet? No idea.
As someone who is not an expert in medicine/biology, every estimate I attempt is going to have a large entropy. Information about this disease we got from various institutions in the past few months was highly biased, because of their incentives. What are the incentives of the people who claim that antivirals look promising? Are the companies just trying to make their product look better, in order to increase the funding provided to them?
The fact that I don't have a clear picture on this bothers me... Where to even get info on this? Are people talking about it but I'm not aware of it? Please, if you have an opinion, leave your subjective probability estimate in the comments, along with the reasoning behind it.
The apocalyptic scenario would surely have huge impact on society. The totalitarian regimes would perhaps deal with this better than free ones, which would either tip the balance of power in favour of China, or it would offer an incentive for the free regimes to turn totalitarian. Even without totalitarianism, a large percentage of the population dying means a lot of people at critical positions (e.g. nuclear power plant engineers) would need to be replaced fast. Also, it means a lot of people at head positions in various organizations would need to be replaced. Will they be replaced successfully?
I hope there is a research group somewhere which is investing, or plans to invest, at least 100 man-hours into investigating the worst-case scenario and estimating the probability of it.