SARS was a flu season virus. It died off completely after the northern hemisphere flu season ended in April/May. That showed that the SARS virus can't use humans as a host reservoir. With humans, it either kills the host or the host kills it. (With bats, it comfortably coexists indefinitely.) It also suggests that it cant shape-change or mutate easily, like to flu virus, to fool the immune system. Consequently, covid-19 (like sars) will likely get hammered by both flu seasons ending and humans acquiring year-on-year immunity to it, and it is unlikely to survive longer than 1 or 2 years with humans, anyway.
