Five years is the maximum sentence, which a person with no prior convictions should easily be able to avoid. Even if the case was brought against a regular person, I doubt there would be jail time. Musk and Rowling can naturally afford the best lawyers, and Rowling has gone radio silent from what I heard. So, fine is easily possible, but jail time is highly unlikely.
Just imagine how hard done by they'll be if they even get the fine. Omg freedom of speech is dead, next they'll get you for thoughts etc etc