Citation needed. The delta variant is the prime counter-example with higher R0 and slightly higher mortality. SAGE admitted SARS-CoV-2 will very likely mutate to defeat all build-up immunity. Variants of SARS-CoV-2 (SARS and MERS) showed the potential to have very high infection fatality ratios.
There is no reason at all to suspect COVID will suddenly become mild.
We need to pay attention to virologists, not HN armchair experts.
Contagiousness can certainly increase. Virulency does not usually increase.
Severe flu seasons are characterized by increased infections, not so much increased fatality rate.
> Citation needed.
"Most viruses become less deadly as they mutate." https://www.economist.com/the-economist-explains/2021/02/27/... (The article is about how COVID might buck the general trend. But in any case, that is the trend.)
My point is that we simply do not know. The word 'usual' is deceptive here. Usual for the viruses we studied? Usual for all viruses? Usual for viruses which recently have made the jump to a new species? We do not know. We simply have no idea.
> no idea
This type of reasoning is based on an assumption that a pathogen limits its reproductive number by increasing its virulence. It is reasonable to test this hypothesis, but unfortunately we do not have enough data points to make any conclusive statements.