… So no, you can’t exactly go to the Gutenberg project and pick up J.K. Rowling’s 8th installment “Harry Potter Finally Sees a Shrink After Suffering PTSD From Way Too Many Near-Death Experiences,” or any of the other seven, but what you can do is look up Arthur Conan Doyle and start reading up on Sherlock Holmes. As far as I know, the Doyle estate can’t stop the Project.
No, they cannot, not unless WIPO and individual nations cave to the demands of the global publishing lobby and render a copyright term to imply Life + Infinity. This is not impossible, but it doesn’t have to be taken that far. To give you an idea, increasing current copyright terms by even 10 to 20 years will pull a lot of books out of the public domain.