1000x times more people died from Covid-19 than SARS. Within three years of the SARS outbreak in 2002, there were already three new strains of SARS. Assuming 1000x as many people were infected by Covid-19 as the original SARS outbreak, it's safe to assume Covid-19 will be around for as long as the flu. That is, there will be a need for annual vaccines.

The more people are infected, the higher the probability of new strains. If the original SARS virus mutated into two different strains within three years, then the probability of perpetually new strains is inevitable. There is already a new strain in the Philippines. The new strain is the dominant strain in the Philippines. https://www.ibtimes.com/entry-new-coronavirus-strain-may-add-philippines-burden-3029547