> It looked for a while there like this could be a thing that gets “done”—that we would get a good vaccine into enough people, then incidence would decline so far it just goes away.

Coronaviruses in general are endemic to humans, and SARS-CoV-2 in particular appears to infect animals. Even if at some point no humans carried the disease, it'd still come back from some cross-species transmission. The only "done" state I ever expected is/was the same situation we have with influenza -- annual vaccine and seasonal waves of illness.