I think Harry, Ron and Hermione will live. I can't see her killing either Ron or Hermione without the other, and I don't think she'd kill both. Not after already killing off so many of Harry's family, real and friend-family. Anyway, you just don't kill off sidekicks in these epics.
Snape. I don't think he's evil. I do wonder if he has his own agenda that's not exactly good but kind of works with the good agenda. I do think he will redeem himself in the end, and I think he will die doing it. Dumbledore's trust of him? I think it leads back to the night at Godric's Hollow. There are *so* many unanswered questions there. How did DD know they'd been attacked and the building destroyed? How did DD know where they were, and how could Hagrid have found it, if Pettigrew was the secret keeper? How did anybody know the course of events if everybody on site except Harry died? How did DD end up with the invisibility cloak? It is my theory that Snape was there under the invisibility cloak, like Harry was on the tower, and alerted DD. Perhaps the Fidelius charm was broken when the people upon whom it was sworn (the Potters) died? So Snape was able to tell DD where it all went down.
Hogwarts: will open, but I don't know if it will remain open.
Horcruxes. Well, JKR has already shot down a lot of my theories: Harry is not a Horcrux. The sorting hat is not a horcrux (that was a popular theory, as it was Godric Gryffindor's). I believe she said that Gryffindor's sword is not a horcrux because it's always been in the headmaster's office. I think something at Godric's Hollow may be a horcrux: JKR has confirmed the theory that there's significance to the word "Godric" in the name. This could go two ways - either one or both, really. That Voldemort made a horcrux there because of it's association with GG, or that the Potters were Gryffindor's heirs. It is highly probable that he *meant* to make a horcrux with Harry's death and failed, but that might mean there's a half-way horcrux of sorts on site there. Moving on from that, I like the theory that Kreacher has one of the horcrux' squirreled away. It would be very ironic that they'd been living with a horcrux that long, in Sirius' house, and never knew it.
Who else dies? Oh, I've been so sad thinking about this. I do think either Hagrid or Molly but not both. I don't think she'd bump off every remaining parental-like figure Harry has. I do think some Weasley will bite it. I hope it's Percy because he's the only one who's not likable
but, I have a feeling that would be too convenient. I think, rather, he'll be a bit more of a tragic figure: he's going to lose a member of his family, and regret treating them all like crap for the past two years. I doubt it would be Bill, since he's already suffered. Could be Charlie, but he hasn't been a well developed character. Again, could be Mrs. Weasley. Or Mr. Weasley. Maybe Ginny or the twins. I could see the twins doing something brash and going out in a blaze of glory. On the other hand, they're such survivors, clever and wily, I could see them making it through. I think McGonagle will die. I feel that was forshadowed when she was hit by all the stunners at the end of book 5, and Madame Pomfrey fretted about her being too old to handle a hit like that.
Other predictions? I think there's something exciting about Ginny. It's obvious that there's something significant to her being the first girl child in the Weasley family in many generations. There's power in being a 7th child. Her brothers have commented on her power - one of the twins said something about her being small but powerful in book 5. The Bat-Bogie Hex quote.
I think Pettigrew will die helping Harry. He owes Harry a blood debt.
I think the veil is the curtain between life and death, and I don't think it can be breached per se... but I think Harry will find he can use it in some way. Perhaps just talking to the dead through it?
I think we'll be learning what Jame and Lily did for a living: I have a suspicion that Lily, at least, worked in the Department of Mysteries. I think she *knew* about the old magic that would protect Harry.
I'm really fascinated to learn what is up with Aunt Petunia. She clearly knows a lot more than she's letting on. She's been in contact with Dumbledore for unknown reasons. JKR has said that she's "all Muggle"... but I wonder how to interpret that? It's been taken to mean she can not and will not ever do magic. But... could one argue that "Muggle" is as much an attitude as an ability? It's said often that Muggles can't see Magical things because they just don't want to see them, they refuse to look, they intentionally look around things that don't suit their world view. Could P have magical ability, but be so Muggle that she represses it? And abject fear for the life of her son will finally break through that barrier? Alternately, there's a really wacky but compelling theory going around that Draco and Dudley were switched at birth; that the real Draco was a Squib and the real Dudley was a wizard, and both families couldn't abide that so Dumbledore or Snape arranged for them to be switched shortly after birth; by that theory, they've been Polyjuiced their whole lives. The person who argues this feels that's the reason for Petunia's obsessive cleaning - that she's freaked out that Polyjuice is being brewed in her kitchen, or is even brewing it herself.
JKR has said that some unexpected person will perform magic. As I argued above, there's still a chance it's Petunia. But I'm actually holding out for Filtch. He's such a sad man, living embittered on the fringes of the magical community, watching all these children performing magic that he doesn't stand a chance of touching. But as bitter as he is toward them, I don't think he'd keep working there if he didn't feel some sort of loyalty toward them, I think there is some deep kind of love and pride there even if he denies it. I bet he'll perform some magic to protect the students.
I think that Neville will definitely come into his own. He's been repressed for so long by his overbearing family, treating him like an idiot, that he'd really believed it; he proved that all wrong at the MoM battle. I think he will continue to grow. There's also a theory going around that Neville had a Memory Charm on him to prevent some awful memory - perhaps that of his parents being tortured? That explained his bad memory and general cluelessness, since it's been established that Memory Charms mess with a person's brain in general. Perhaps that charm is wearing off? Is he going to remember something really crucial?
Other creatures: I really want to know if Hermione's ever going to succeed in freeing the house elves. Will the conflict between Firenze and the rest of the centaurs come into play? How about the goblins? It's been said that their loyalties are kind of a mystery. And Grawp? Will the werewolves gain any respect, despite the efforts of Greyback?
Ollivander: I think he's a Death Eater. At the beginning of book 1, when Harry bought his wand, Ollivander tells him that it's very curious, because the phoenix that gave the feather to that wand gave only one other feather, and that one went into Voldemort's wand. Er... how did he know that? Voldemort would have been Tom Riddle when he bought his wand. Purportedly, nobody except Dumbledore knew that Voldemort used to be Tom Riddle. So how did Ollivander know that Tom Riddle's wand eventually wound up being Voldemort's wand?
But, Ollivander didn't show up at the graveyard in book 4. Voldemort said then that there were three DEs missing: one who was on the run, one whom he feared would never come back to him, and one who was his true servant doing his work. By the end of that book, you presume the first is Karkaroff, the second Snape, the third Crouch. I cannot help but think that JKR purposely planted that there to confuse us. Perhaps he wasn't mentioning Crouch at all because he knew all the other DEs assumed him to be dead? In that case, was Ollivander one of the three missing DEs he mentioned? If so, which one? If we continue to assume that Karkaroff is the one on the run, is Ollivander the faithful servant? Or is Snape? I think Voldemort thinks Snape is his faithful servant, and Ollivander is the one who will not come back.