Robomatic, YOUR QUESTION IS VALID. Just like the flu is endemic every winter season, Corona virus has a similar potential to always be among us. It is NOT likely Covid 19 could be eternally endemic.
There is hope we will eventually create a one vaccine - cures all flu mutations.
As long as we dare speak of worst case scenarios remember we as human beings have reduced ourselves down to only one species. Many millenia ago we had 4 or 5 different human species. Most outbreaks are species specific.