I half expect that. Like Robert Jordan before him, Martin doesn't appear to be in the best of health. Brandon Sanderson made a heroic effort to salvage Jordan's "Wheel of Time" series and pulled it off to a degree, but it had already spiraled into way too many open plot lines and most of them had to be ended in a way that was unsatisfactory to the long-time reader. Authors who attempt such massive tales should really write them in a serial form, with each book a complete story that can stand on its own.
But I'm still amazed Game of Thrones got made for TV at all, and even more so that it has remained fairly true to the books thus far.
I agree with everything you said in your post. They have remained very true to the books. It is costing a fortune to produce and they have spent the money very well. The quality of the production shines in every scene. They have also done a marvelous job picking the actors for the various roles and the actors are doing an exceptional job fleshing out the characters and portraying them on the screen. I just wish the author didn’t make it his seeming over-arching goal to kill nearly every “good” and decent character he can. It is very disheartening and as a result it makes it hard for the reader to stay engaged because most of the characters left by the end of book five are hard to care about or root for because most of them, with a very few exceptions are schmucks. It is like being forced to root for someone in the Obama Administration because there are no men of honor and decency left. What is the point? They are ALL nefarious!