yeah, that is what he said before. About two weeks ago rumors started circulating about the 8th book. Check on-line, you'll find all about it.
But TV show won't be longer than 8 seasons, the producers told it in complete confidence. In some article it was mentioned that they went to GRRM and discusses fates of the characters, and the ending of the series. So the last FOUR seasons will be very condensed and heavily modified.
By the way, it won't surprise me if GRRM will drop dead before publishing even book 5. He is old, and I doubt that in good health. About the rest - well, guy is doing tours all the time, and he refuses to write anything when he is not in his house, at his DOS computer. I wouldn't hold my breath about series being finished in book form. But at least we'll have HBO.