They've already said that they will kill off a character in the first season that doesn't die in the books until book three. I assume that's what Martin is referring to, and Venardhi's theory that it's Hoster seems pretty solid - it could be a throwaway line in one of the last two episodes.
I don't think the slight difference in Sansa's story is that important, really. She's still just as taken with Joffrey and the Lannisters as she was in the novel.