Well, we're about two weeks out from the massive THUD of Harry Potter and the Deathly Hallows, which I will of course buy on day one and read as quickly as I can. I actually haven't re-read any of the previous volumes yet, but I suppose I will sometime once the series is complete. So, since I'm not totally "up" on my Potter-verse mythology, I'm not equipped to speculate a lot on what's going to happen.
However, I will note that I'm keenly interested in seeing how two specific characters -- well, groupings of characters, anyway -- ultimately fit into the story. Sure, I want to know if Harry dies and what happens to Ron and Hermione and Hagrid and so on, but the two supporting-cast character arcs that most interest me are Neville Longbottom's and the Dursley family's. Neville's got to have some important task to accomplish -- maybe he's the next Dumbledore! -- and I can't fathom that JK Rowling has kept the Durleys around just to have them be irrelevant in the end.
Oh yeah, and Peter Pettigrew's life-debt to Harry Potter needs to come into play at some point, I suppose.
And here's a question: I wonder if Rowling will ever write another word after this.