What we know will happen:

• We will find out what Dudley saw in Order of the Phoenix when he was attacked by the dementor.
• We will find out the true identity of R.A.B., though most fans are quite sure it's Sirius's brother, Regulus.
• We will see Viktor Krum again.
• We will find out a little bit more about Harry's Grandparents.
• We will find out what happened to Sirius' flying motorcycle, "but the real sleuths among us might be able to guess." Care to hazard a guess?
• Wormtail's life debt to Harry will come into play, somehow.
• We will find out what Lily and James did for a living. This piece of information is "important to a later plot." Possibly something Harry finds out during his visit to Godric's Hollow?
• The shroud that surrounds Snape will fall and we will see where his loyalties truly lie.
• One of Harry's classmates will go on to become a teacher, but it isn't "maybe the one you think, hint, hint, hint," and it isn't Ron, either. Our guess is Neville, but we'll see!
• We will find out something extremely important about Lily and James and it will have a direct effect on what Harry has to do. And no, conspiracy theorists, it's not that they were actually both working for Voldemort, an idea that sickened Ms. Rowling (see below).
• We will see Dolores Umbridge again.
• We will see Rita Skeeter again. At the Edinburgh Book Festival, Rowling had this to say: "I actually quite like Rita. She is loathsome - morally, she's horrible - but I can't help admiring her toughness. She is very determined to do the job and there is something quite engaging about that. There is more to come on Rita."
• The last word of the book is "scar," though that may change with future edits.
• We will find out something "incredibly important" about Lily Potter.
• Harry's eye color will come into play. Also, JKR said that "he has his mother's eyes and that's very important in a future book."
• There is "more to the Sorting Hat" than what was presented in the first six books; we will "find out what it becomes" in book seven.
• Although Aunt Petunia is neither a witch nor a Squib, "there is a little bit more to her than meets the eye," and we will find out what that is.
• According to Jo, "one character got a reprieve, but I have to say two die that I didn't intend to die. A price has to be paid. We are dealing with pure evil. They don't target the extras, do they? They go for the main characters, or I do."