What about Dean Thomas? On JKR's website she says that she cut his story from SS/PS and CoS and that story was that he had always thought himself to be muggle-born but in actuality his father was a wizard who was killed by Death Eaters when he refused to join Voldemort.
He's a Gryffindor who's always just kind of there in the background. Maybe we'll finally get to hear his story and he will be a key ingredient in Voldemort's undoing...Or maybe there is another prophecy about a HBP and Voldemort gets really confused and kills Dean and this makes Harry really angry and he goes after Voldemort and they duel again, except maybe Voldemort uses Dean's wand so there's none of that brother wand interference. Of course Harry will escape, but it will be close....