Highly improbable, but not impossible, particularly for beings with finite lifespans over the long term. Herd immunity is reached at HIT=1-1/R0, at which point the infection rate will slow, and some of the remaining uninfected and unvaccinated individuals will have avoided exposure, as the chain of transmission to them will be broken. Back at the start of COVID-19, that would have been a sizable percentage of the world, though now (due to the higher R0 for delta) it is a much smaller percentage of the population who can escape exposure in this way alone.

And note that R0 can be changed by altering some environmental factors in the formula above.