Whichever way it turns out it'll really be a landmark case. If the author/publishers of the new book win, that would finally secure fan fiction (as I imagine similar concepts are involved, and furthermore fan fiction is one giant step removed from this by its non-profit nature). That, in turn, provides a legal basis for fan art, and maybe even fan gaming someday.
I might be wrong, but I'm seeing importance of Roe v. Wade proportions here.