But now we're making assumptions on the peak virulence of covid. Why does Delta have to be the "truly deadly one?" The flu varies significantly year to year with severity. Zika, hep B, myxoma, etc. These all took years to evolve to increased virulence and many folks likely "called the top" well before virulence peaked.
I mean I would hope Delta is peak virulence but what evidence is there? If omicron is only 20-30% less virulent because it doesn't thrive in your lungs last past variants, there is clearly a lot of room for that lung bit to change in the evolutionary chain. I hope it doesn't and I hope that increased transmission depends on it being a primarily upper respiratory virus. But that's just a theory based on hope; predicting evolution is hard.