It depends on multiple factors. The quickest way for a virus to mutate is by rapidly infecting multiple hosts. That is one of the primary reasons to stop the spread in it's tracks, so we don't get truly deadly mutations manifesting.
Ark831 is correct it is already a mutation and will most probably continue mutating. The more hosts/infected there are the greater the likelihood of further mutations.
seems like it is mutating, but only 1-2 nucleotide changes so it doesn't seem like it will make a bit shift. also since it is so infectious, it is unlikely for it to go back towards the SARS direction of low infectivity but high mortality (it would want to spread/survive more than mutating for lethality).