You know, I can see Hermiony (?) or Ron being killed off: what better motivation for Harry to actually kill a "live" person? Could push him over the edge into some dark stuff and cause lots of damage.
I can also imagine a lot more dueling and wand work in this one. And I think that Harry will be walking about the muggle world, rubbing shoulders with them and either being hunted or hunting something. And I think that Dumbledore will show a nasty/ruthless streak and perhaps explain what he's done to Harry's blood to track him.
It's almost as much fun speculating as reading
