I think GRRM can finish book 6 by the end of this year or perhaps early 2016. He has released several sample chapters already.
I read that he says he is making more negative progress than positive progress.
Basically he writes something, then spends days unwriting it and rewriting it.
I hope he’s not trying to make it too perfect. None of the books are perfect I’d say. What makes them great to me is the depth of the characters.