Fans have invested in a story. They started a book, got a second book, got a couple short stories and promises of a 3rd book. No 3rd book has arrived to complete the story.

If he had said "sorry, no book 3, it's just done now" years ago, or even now, then that changes expectations. But if he's just going to avoid it all then ya, that's kind of a bad thing to do to your fans.