The bigger picture in Rowling vs. RDR is not just the publication of material generated by fans of an author's work, but the issue of Fair Use.
Co-counsel Julie Ahrens, associate director of the Fair Use Project explains that "Fair use protects scholars' rights to create such companion guides [like the Harry Potter Lexicon]. It simply is not the case that authors can exploit copyright law to prevent analysis and commentary on their work." If Warner and Rowling win, it could set a dangerous precedent for authors to invoke copyright infringement on any work, from reviews to companion guides that they don't agree with. Just imagine the New York Times being sued for a negative review because it cites material contained within a novel, and the author wants to be compensated for loss of revenue because of it. It's a 1984 double plus good scenario, but stranger things have happened.