1) Harry/his scar is a horcrux. It’s clear as day. It also seems clear that Voldemort didn’t intend for it to be, but it happened anyway. Although there’s no record of accidental horcrux-making, the conditions were ripe, Harry was protected from death by his mother (‘Deathly Hallows’?), and the prophecy said that he would ‘mark him as his equal’. Also, the fact that ‘none can live while the other survives’ means that neither has known wholeness of identity since their first encounter. This leads me to my next prediction:
2) Harry will not die as a result of the destruction of the horcrux that is somehow a part of him. Rather, he will become a Squibb. Although JKR has denied it, I thought it would have been fitting for Squibb Harry to return to Hogwarts to teach Defense Against Dark Arts, having broken the jinx on the position and shown a great aptitude in both performing and teaching the subject. Alternatively, he’ll work for the restructured Ministry of Magic…
3) As I reread all of the books, I am noticing the very strong theme of xenophobia that runs through the wizarding community. It is most acute with the Slytherins and their obsession with ‘yiches’ (lineage), but really runs right through the entire ministry. The statue at the entrance to the ministry building really sums it up – werewolves, centaurs, and house-elves adoring a wizard. The suspicion against any ‘half-breeds’ is another clue. The final episode will see the dawn of a new order in the MoM, and Hermione will play a key role in that. As annoying as S.P.E.W. is, it will turn out to be the basis for much more far-reaching reforms. The reformed ministry will have various non-humans and half-breeds sitting on its Wizengamot – including giants (or half-giants), goblins, elves, centaurs, and werewolves – perhaps even a Squibb (Harry, by the end?) and a Muggle (Aunt Petunia?). Candidates to be minister are: Hermione (perhaps in the Epilogue; she’s too young during the book), Remus Lupin (helluva way to overcome unemployment, and he has the right temperament), Professor McGonagall (unless she’s Hogwarts Headmistress), and the, erm, dark horse pick,
4) REB is Regulus Black – duh. The locket is in the possession of Mundungus Fletcher, who stole it from
5) The following is a list of characters who will be killed, kissed by dementors, or otherwise knocked permanently out of commission (like Lockhart or the Longbottoms): Voldemort, Bellatrix Lestrange, Snape, Hagrid, Peter Pettigrew, Bill Weasley (I don’t think JKR can resist a hysterical Fleur).
6) Snape has remained loyal to Dumbledore, who is really dead. When push comes to shove, Draco will be unable to become truly evil (though, as is often repeated, the world is not simply divided into good and evil, and Draco is certainly not good). Harry will collect his debt from Peter Pettigrew.
7) Voldemort will meet his demise through a dementor’s kiss. I believe the dementors will have a role in the dectruction of the horcruxes as well; Hary et al will discover that their soul-sucking abilities and desires can extend to horcruxes as well. I wonder if that’s how Harry rids himself of the scar…
8) The couples remain intact – Harry and Ginny, Ron and Hermione, and probably Neville and Luna.
9) Neville will get his revenge against Bellatrix, but then be sorely tempted to join Voldemort, having begun to feel his own power and gotten sick of being second-tier behind Harry, Ron and Hermione (much like Peter with regard to James, Sirius, and Remus). Unlike Wormtail, however, Neville will resist the temptation.
10) We will read about the nature of the soul, the afterlife, what lies behind the black veil, and why Harry didn’t die.