I think it’s probably happening already & we don’t realize it.
I know of a community-acquired infection in a mid-Atlantic state that when they sequenced it compared to their reference strain from Washington state, it was noticeably different. It wasn’t the same or just 1 mutation off, it had multiple mutations differences.
The strains that have been sequenced so far seem to have a highly conserved spike protein. Basically, a lot of the mutations are not occurring in the protein that binds to our cells. There are several mutations though that allow us to trace the evolution path. If the strain is sequenced, you can tell if the lineage was China to West coast or China-Italy-New York. I am sure there maybe other evolutionary paths.
We know this virus has 29 proteins. A mutation in the RNA may be silent (doesn’t change much) or it could be significant. As these strains evolve, we could definitely have a SARS-CoV-2 strain circulating that is infectious but not very pathogenic and basically acts almost like a vaccine strain. We could have one mutate into a more virulent or pathogenic. We may have it eventually evolve to where at catching 1 may not provide protection to another strain. We don’t really know what’s happened. In a perfect world, a highly contagious, less virulent strain emerges that infects everyone, causes a robots immune response and then people are protected against other strains because they haven’t evolved so much yet. The virus is remarkably stable for having passed through so many people, but we really don’t have a full picture on the evolution yet - we just keep getting small pieces of the puzzle.