His publisher also came out a few months ago saying she hasn't seen one page yet from book 3, and said she didn't believe he had written anything. I don't think he ever responded. And yes, his pet charity seems to take all of his time, which appears to be an excuse from having to fight through writers block and finish the book (or start writing the damn thing?)
My brother gave me the first GOT books back around 2007, bringing me into a world of great books that never finish. I gifted him the first two Kingkiller Chronicles as payback.

It has been so long since I read any of them, I don't really care if they every get finished to be honest. And both are fat, unhealthy people that will likely die (GRRM is 72, so he'll probably be gone within the next few years, so no way that gets finished). Rothfuss is 48 and has one book to write, so it may get finished within the next 25 years. I'll have to decided if I want to re-read the first two if the third is ever released. Supposedly he wrote the whole story when he was young in a rough form. Book two was said to be written when book 1 was released, yet it took forever for it to come out. GRRM had a similar thing with the last two book (written at the same time and took a decade to edit book 2, which is insane).
I didn't read the last GOT book, and don't plan to read anymore.
I like the writing philosophy of Sanderson much more, who plots out the whole series in an outline before he starts writing. He fills in gaps, but knows the larger story, so there are fewer plot holes to fill. GRRM figures it out while he goes (with a general idea of how it goes, but not fully plotted out). There are so many side pieces that it is daunting to try and put it all back together.
I have to think if I am an author (can't blame GRRM, he is 72 and a multimillionaire thanks to HBO) like pre-tv GRRM or Rothfuss, that I'd dedicate enough time to get books written in a reasonable period of time. Fantasy is ok, but is down the list of my regular reading preference, but some of this more recent authors have made decent books, but I don't have the memory or time to wait 10 years between books as I'd have to go back and re-read the original stories to remember what the hell was going on after 10 years.