I don't know about the horcrux being IN Harry, but I would bet that Harry is going to have to make a hard decision while searching for the horcruxes. Like: let a close friend die or kill Voldie. I know, thats a little vague, because the whole book will probably be full of hard decisions Harry has got to make, but that's all I've got.
I think Snape has displayed too much bad aura that it is kind of irreversible right now. He has let good people die, so that automatically makes him bad in my mind. I don't think he could do something good enough to suddenly become a "good guy".
New question: Do you think any of Harry's friends will die? Much has been said about perhaps Ginny dying, or maybe Ron Weasley. I think there is a good chance that Ginny will die... how about you?