Viruses (usually) trend towards being less deadly, as this is how they can become most infectious and create the most copies of themselves. Hence why we deal with influenza year in year out, which isn’t very deadly but extremely persistent and easy to pass between people. Killing the host is simply a side effect of viral replication, not a “goal” that the virus has, it’s really not beneficial at all. The quicker it kills someone and the more severe the side effects of infection, the less likely that person is to be moving around and actively spreading the virus. So in short, yes, you’re right!
Short term though, anything can happen. There could also be an isolated version that kills at a higher rate but at the same time spreads less effectively, like some of the more recent influenza outbreaks (not a direct comparison). Who knows, coronaviruses have large RNA genomes that are notorious for high mutation rates so it’s anyone’s guess.
Disclaimer: any knowledge comes from a generic Biochemistry degree, not an expert.