Honestly when I saw that he couldn't even finish or sound confident after the show's finale butchered his characters and potentially killed the series? That's when I felt like ok it might be over. I still think TWOW comes out but I just can't imagine him finishing the series. And I think he's too scared to admit he can't do it in seven books.
You can't be stuck at 60-75% for a decade, which is what's happened here...unless you have too much material with no end in sight. I think he's got way too many chapters and once again isn't listening to his editor. The pacing of AFFC/ADWD is extremely slow and plodding compared to the first three books because he refuses to skip time. He uses travel chapters to build lore, which is fine. But you cannot do that in half your POV chapters. For instance if you've read the TWOW sample chapters...Arianne has two chapters. In the first one we learn she's traveling to meet "Aegon" and Connington. There's a boat ride, a travel through a forest, some caves, etc....and by the end of the second chapter she still hasn't met either person. This could have been one chapter that ends with her arriving in her location and preparing to meet them. It's just a waste of pages....now imagine that pacing across an entire book, with all the POV characters he has. It's impossible to do that and reach a climax/conclusion within 900 pages.