George R.R. Martin seems to have to constantly confront questions, not only about when his next A Song of Ice and Fire novel will be out, but also deal with discussions about what might happen to the series if he doesn't complete them before... well, you know. Recently he has said that he will not allow another writer to play in his sandbox when asked about licensed work.
Not while I'm alive, but eventually I will not be alive because Valar Morghulis – all men must men die.He goes on to talk about his dislike for fan-fic and his belief that writers should spend their energy creating their own characters and world to write about. He even want so far as to call fan fiction itself "lazy." He did admit that Westeros may not die with him, (despite the many other stories out there I've seen saying differently).
I don't think my wife, if she survives me, will allow that either. But one thing that history has shown us is eventually these literary rights pass to grandchildren or collateral descendents, or people who didn't actually know the writer and don't care about his wishes. It's just a cash cow to them.
I could go on about the fact that I've seen too many stories talking about what will happen if Martin doesn't complete the series, saying he will not allow it to be finished by another. But it's a ridiculous discussion for several reasons. One, he didn't actually say that. Two, you never know what might change over the coming years. Three, he won't be in control of his estate once he's gone. And four, HE WILL FINISH IT!
Stop worrying, he's got this.
Just be aware, if you're bored while you're waiting for Winds of Winter, don't pass the time writing Game of Thrones fan-fic. Let's not anger the man, he's running out of Starks to kill.