They don't need him at this point, as long as they got the gist of the stories as far as an ending goes they are fine. They already deviate enough from the books to be its own separate entity really. Just have a few more seasons then end it and move on to Dunk and Egg and whatever else they are planning, this money train is going to keep on chugging regardless if he ever finishes the damn books so I doubt they even care lol. Only the book readers are somewhat pissed that the show will spoil some of the plots but so what, I'm a book reader and I don't care, he's never going to finish anyways and when he dies I bet those hardcore GRRM fans that run that Westeros website will finish it for him, I mean GRRM checks with them for fact checking and whatnot as it is, they seem to know more about his universe than he can remember.