In an interview with the New York Observer in August 2015, Martin shed some light on how he plans to end the books, and since he and the showrunners seem to be on the same page, you can expect the ending of the show to have a similar tone:
"I haven't written the ending yet, so I don't know, but no. That's certainly not my intent. I've said before that the tone of the ending that I'm going for is bittersweet. I mean, it's no secret that Tolkien has been a huge influence on me, and I love the way he ended Lord of the Rings. It ends with victory, but it's a bittersweet victory. Frodo is never whole again, and he goes away to the Undying Lands, and the other people live their lives. And the scouring of the Shire — brilliant piece of work, which I didn't understand when I was 13 years old: 'Why is this here? The story's over?' But every time I read it I understand the brilliance of that segment more and more. All I can say is that's the kind of tone I will be aiming for. Whether I achieve it or not, that will be up to people like you and my readers to judge."
