Both books that have outsold the Harry Potter series claim divine authorship, not purely human. I am prepared to bet quite a lot that the next isn't human-written, either.
I don't know. It's a question relevant to all generative AI applications in entertainment - whether books, art, music, film or videogames. To the extent the value of these works is mostly in being social objects (i.e. shared experience to talk about with other people), being able to generate clones and personalized variants freely via GenAI destroys that value.
You may be right, on the other hand it always feels like the next goalpost is the final one.
I'm pretty sure if something like this happens some dude will show up from nowhere and claim that it's just parroting what other, real people have written, just blended it together and randomly spitted it out – "real AI would come up with original ideas like cure for cancer" he'll say.
After some form of that comes another dude will show up and say that this "alphafold while-loop" is not real AI because he just went for lunch and there was a guy flipping burgers – and that "AI" can't do it so it's shit.
https://areweagiyet.com should plot those future points as well with all those funky goals like "if Einstein had access to the Internet, Wolfram etc. he could came up with it anyway so not better than humans per se", or "had to be prompted and guided by human to find this answer so didn't do it by itself really" etc.
Most human-written books don't do that, so that seems to be a ceiteria for a very different test that a Turing test.