The movies may help Ltor a lot more than Harry Potter movies. Peter Jackson changed narratives elements, but was very faithful to the visual, fans still can watch it in the same way they keep the illustrations. And Tolkien movie had a lot of power drawn from imagem and not text. This is not the case of Harry Potter, who will last more probally due the fan-made writtings, etc., sort like Sherlock Holmes who is bigger than all his books.