That's purely speculation at this point, while epidemiology shows us that viruses which are more fatal tend to be less transmissible and vice-versa.
"""The trade-off model recognises that pathogen virulence will not necessarily limit the ease by which a pathogen can transmit from one host to another. It might even enhance it. Without the assumed evolutionary cost to virulence, there is no reason to believe that disease severity will decrease over time. Instead, May and Anderson proposed that the optimal level of virulence for any given pathogen will be determined by a range of factors, such as the availability of susceptible hosts, and the length of time between infection and symptom onset.
There is little or no direct evidence that virulence decreases over time. While newly emerged pathogens, such as HIV and Mers, are often highly virulent, the converse is not true. There are plenty of ancient diseases, such as tuberculosis and gonorrhoea, that are probably just as virulent today as they ever were."""
Right and our vaccines have maintained efficacy against these things.
> It's also not a guarantee that the virus will evolve into something weaker
No but it is almost certainly the case if the past is anything to go on