High mortality rate is typically a negative factor in disease spread, but it's somewhat nuanced. For example, stuff like incubation period plays a role as well. If it's deadly in the end, but it takes a while for a person to get to that point, they can go on infecting a lot of other people before they realize they're sick. The virus will also continue to mutate, so a less deadly variant might emerge that's better at spreading. Very difficult to say what will happen at the moment unfortunately.