- This is a placeholder until the book is released! This information was taken from Wikipedia.
Known plot details
Unresolved plot elements from previous books
* Harry will return to the home of his non-magical (Muggle) relatives, the Dursleys, during the school holiday. The magical protection Albus Dumbledore arranged, which requires Harry to have a home with them, is set to expire on Harry's 17th birthday July 31.
* Harry plans to visit the remains of his parents' home at Godric's Hollow. Ron Weasley and Hermione Granger plan on accompanying him on this trip.
* Bill Weasley and Fleur Delacour plan on getting married in August. Several of the main characters have been invited.
* It is unclear what will happen to Hogwarts after the attack on the school at the end of book six, but Harry has said he will leave school to continue his battle against Voldemort. If the school reopens, new instructors will be needed for Defence Against the Dark Arts (replacing Severus Snape), and possibly Transfiguration in the event Minerva McGonagall becomes Headmistress.
* Harry comes of age (for wizards) when he turns 17, and is therefore entitled to perform magic outside of school and to obtain a licence to Apparate. His friends Ron Weasley and Hermione Granger, and many of his classmates, already turned 17 during the sixth year, and Neville Longbottom turns 17 on July 30 - the day before Harry does.
* There is no explanation at the end of Half-Blood Prince as to the true identity of the mysterious "R.A.B.", who claimed to have stolen one of Voldemort's Horcruxes with the intent to destroy it, while replacing it with a fake that was recovered by Harry and Dumbledore.HBP Ch.28 The most likely candidate is Regulus Black, who Rowling said was "a fine guess" for R.A.B.'s identity in an interview. Also in book 5 when cleaning out the cupboards in 12 Grimmauld Place Mrs. Wealsey finds a heavy locket that she was unable to open.
* Because Harry convinced Remus Lupin and Sirius Black to spare Peter Pettigrew's life in the third book, Pettigrew owes Potter a yet unpaid life debt.
* The quest to identify, locate, and destroy Voldemort's remaining Horcruxes will continue. The remaining Horcruxes must be destroyed before Voldemort can be successfully conquered.
* Harry will have his final battle with Lord Voldemort by the book's end.
Information from Rowling
* Rowling wrote the last chapter of the book some time ago, to give her an ending to work up to. The last word of the seventh book, according to Rowling, is currently "scar" , but she has also said it may change, along with the whole last chapter she has previously written. This last chapter contains details of what happens to each surviving character:
"This is the thing that I was very dubious about showing you... This is the final chapter of book seven. This is really where I wrap everything up, it's the epilogue. And I basically say what happens to everyone after they leave school - those who survive - because there are deaths - more deaths coming. It was a way of saying to myself, 'Well, you will get it, you will get to book seven one day. And then you'll need this!' So I'd just like to remind all the children I know who come around my house and start sneaking into cupboards that it's not there anymore - I don't keep it at home anymore for very, very, very obvious reasons. So there it is." – J. K. Rowling
* Rowling has stated that there will be no Quidditch matches in Deathly Hallows.
* J. K. Rowling said in 2001 that Harry might get another pet at some point. Although Buckbeak may have filled this role (Harry obtained possession of the Hippogriff after the death of Sirius Black, albeit under Hagrid's care), she also hinted that Fawkes, Dumbledore's phoenix, might have another role.
* We will learn something very important about Lily:
Now, the important thing about Harry's mother - the really, really significant thing - you're going to find out in two parts. You'll find out a lot more about her in book five, or you'll find out something very significant about her in book five, and you'll find out something incredibly important about her in book seven." – J. K. Rowling
* Rowling has long said that the fact that Harry's eyes resemble his mother's is important.
* Severus Snape has been an important and enigmatic character throughout the books, as his true loyalty has always remained unclear. It is to be anticipated that as a surviving major character, his loyalty will be settled in the final confrontation of the book.
Questioner: There’s an important kind of redemptive pattern to Snape.
Rowling: He, um, there’s so much I wish I could say to you, and I can't because it would ruin. I promise you, whoever asked that question, can I just say to you that I'm slightly stunned that you've said that and you'll find out why I'm so stunned if you read Book Seven. That's all I’m going to say.
* She has stated we will learn more about Peter Pettigrew and Dumbledore and their respective families.
* At the Edinburgh book festival, Rowling mentioned that something more would be revealed about Petunia Dursley. Nothing of note occurred in book 6, so this remains to be discovered.
"..there is a little bit more to Aunt Petunia than meets the eye...She is not a squib, although that is a very good guess. Oh, I am giving a lot away here. I am being shockingly indiscreet."
Rowling repeated this comment at the Radio City charity reading in August 2006.  She clarified by stating that Aunt Petunia will not perform magic.
* Rowling has said that some non-magical character will perform magic late in life in desperate circumstances. However, Petunia will not be the one to perform magic (see above).
* Also at Edinburgh, Rita Skeeter was mentioned: "She is loathsome . . . but I can't help admiring her toughness. . . . There is more to come on Rita"
* On Dolores Umbridge, "It's too much fun to torture her not to have another little bit more before I finish"
* Rowling has said that Ginny Weasley is quite powerful, that we have seen a taste of that in the past, and we will see it again. 
* Viktor Krum is set for a reappearance.
* Kreacher, the former Black Family house elf which passed to Harry's ownership with the death of Sirius Black, may make an appearance. Rowling told the filmmakers of Order of the Phoenix to include the character in the movie, because he is "very important". 
* The two-way mirror given to Harry by Sirius Black and his flying motorbike will return. In fact, Rowling has mentioned in one of her FAQs that the two way mirror "will help more than you think". Rowling refused to comment whether Sirius himself might in some way reappear, but she has also said that there was a reason why he had to die.
* Rowling refused to comment when asked whether the locked door in the Department of Mysteries in the Ministry of Magic would feature in the final book.
* Dumbledore was said to have a "gleam of triumph" in his eyes when told that Voldemort had restored his body using Harry's blood, at the end of Goblet of Fire (Ch. 36). Rowling has confirmed that this is "still enormously significant".
* Someone from Harry's class--not Harry, Ron, or Hermione, and not who most readers would expect--will become a Hogwarts teacher. This seems to indicate that Hogwarts will indeed re-open, though possibly not until after the main events of Deathly Hallows have occurred. 
* In an interview after the completion of the Prisoner of Azkaban film, she commented that director Alfonso Cuarón had "put things in the film that, without knowing it, foreshadow things that are going to happen in the final two books. So I really got goosebumps when I saw a couple of those things, and I thought people are going to look back on the film and think those were put in deliberately as clues." 
* There are indications that at least two of the main characters will die. In a June 2006 interview about the previously-written ending, Rowling stated that:
"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 go for the main characters... well, I do".
* When further questioned in June 2006 about authors who kill off their main characters, Rowling said "I can completely understand, however, the mentality of an author who thinks, well, I'm going to kill them off because that means there can be no non-author-written sequels'".
* Rowling clarified that "Dumbledore is definitely dead", when asked by Salman Rushdie and others at Radio City Music Hall in New York City. Rowling answered the same question three times, each time with increasing conviction.. However, on the set of the Order of the Phoenix film, she remarked; "Dumbledore's giving me a lot of trouble". When asked "But isn't he dead?" by Daniel Radcliffe, she explained; "Well, yeah, but it's more complex ...".
* When asked what questions she should have been asked, she admitted that "the final book contains a couple of pieces of information that I don't think you could guess at", and declined to explain further. On 13 September 2006 she updated her website saying that when she was asked that question, her mind went blank. Since she couldn't make amends, she created a NAQ section of her website, in tribute to the girl who asked the question. In her NAQ section, she states:
"Why did Dumbledore have James' invisibility cloak at the time of James' death, given that Dumbledore could make himself invisible without a cloak?"
On 29 September 2006, she revealed that Severus Snape was not under the cloak the night of the Potters' death in the Rumors Section.
* Asked which five of her characters she would like to invite to dinner, she chose Harry, Hermione and Ron, but then hesitated before choosing her last characters, saying "See... I know who's actually dead", unsure whether she was permitted to invite those who are 'dead'. 
* Lord Voldemort was voted best villain at the Big Bad Read poll. Responding to the news Rowling commented:
"I hope those of you who voted for him in the big bad read enjoy reading about him in book seven, where he finally gets the leg room for which he has been aching all those years in exile."