Martin had previously released a chapter from the upcoming novel last year, told from the perspective of Theon Greyjoy. Unfortunately for fans, the chapter Martin released yesterday will not be an additional chapter to the novel, but instead a replacement for the Theon's chapter. Told from the perspective of Arianne Martell, Princess of Dorne.
Martin has also recently made several blog posts about how much he is currently toiling away at the next book, so fans may not have as long of a wait as they did between books four and five. I'm sure the looming hit television show catching up to his books each year adds additional pressure.