The issue isn't that Airbnb or anyone needs to be able to predict anything related to COVID-19. The issue is that Airbnb needs to make 100% clear and WITHOUT any chance of alteration, who will bear the risks going forward.
I think Airbnb should make a big giant obvious declaration that, from now on, no more changes to the cancellation policy will be made in regards to COVID-19. The entire world is aware of the situation. If someone wants to make a booking now, they take on the risk as they see it.
If Airbnb wants to make the opposite declaration and tell everyone that cancellation policies will continue to mean nothing going forward, then we all know what we need to do (stop using the Airbnb platform as hosts).