I mean, any immunity that is seasonal or unable to be vaccinated against and I don’t see how anyone can reach an even remotely positive conclusion that doesn’t involve the decline of society as we know it.
I dont think its deadly enough to to significantly affect population numbers. Its just that we cant have the response that we have now, we will just have to deal with it wear masks and accept that we are 2x as likely to die in 2020 than we were in 2019. Ideally we would build up hospital and funeral capacity to account for the increased mortality and that would be that. In reality things seem to be going the other way in we are instead decreasing hospital capacity so who knows.
It's definitely bad if that's the case, but I think it will be adaptable if we can get cheap, reliable, fast, widely-deployed testing. It would take a really big social commitment, but I think we're up to it. As much as quarantine sucks, all but the worst among us are taking it in stride, so I think we're capable of more than we think we are.