•  Hagrid is not the HBP - two seperate fans have reported to Mugglenet that when asking JK if Hagrid was the HBP she said no on both accounts.

Rumours that have been killed by JK

• Mark Evans is not important to the plot he is just a fly by character that is just mentioned in passing and that he and Lilly have the same last name is pure concentance.
• There will be no character named "Icicle," and JK said that she didn't recall saying there ever would be.
• Dumbledore is not a relative of Harry
• Harry is not related to Voldemort and he is not related to Salazar Slytherin.
• Lily Potter is not alive.
• Lily was not a death eater
• No prequel books are planned (no books before Harry's time at Hogwarts)
• Crookshanks is not an Animagus
• Neville is not the son of Peter Pettigrew (where do these people come up with this stuff?!)
• Remus Lupin does not have a twin brother.
• The next book with not be called "Harry Potter and the Green Flame Torch" or "Harry Potter and the Mountain of Fantasy"
• JK does not have any parts in the films
• Harry Potter will not be the new Minister of Magic

Facts

These have been all confirmed as true for the numerous places I have gathered information on.

• We have a future character describiton that is pure fact according to JK herself: The first line said: "He looked rather like an old lion." It went on: "There were streaks of grey in his mane of tawny hair and his bushy eyebrows; he had keen yellowish eyes behind a pair of wire-rimmed spectacles and a certain rangy, loping grace even though he walked with a slight limp." Who can it be?

• By the ends of books 6 and 7 "you'll have all the back story you'll need", says JK Rowling, and a prequel will not be necessary

• There will be a new Minister of Magic, no more Mr. Fudge. Although JK has not confiremed which book she will get rid of the useless idiot!

• We will find out what happened to Hagrid's half brother Grawp. He will be a bit more controllable in book 6.
• The Dursleys are in the next book, but Harry's stay with them will be the shortest yet. In book 5 he stayed for 4 weeks, so we know his stay will be less than 4 weeks.
• Cho Chang will not be a romantic interest of Harry in Book 6, however there will be a "little romance" for Harry says JK.
• In books 6 and 7 we will find out exactly why JK killed off Sirius.
• Harry becomes even more powerful in book 6. (Which is aout time in my opinion!)
• In books 6 and 7 we will find out why Dumbledore trusts Snape.
• We will find out what happened to Wormtail AKA Peter Pettigrew
• More about the animosity between Snape and Sirius will be revealed in the last 2 books.
• JK has said that giving away the form of Snape's boggart and patronus says too much. We'll definitely find out what Snape's worst fear is, and it'll be important.
• Hermione and Draco will NOT end up together in book 6 or 7. Which is a killer for all those Hermione/Draco shippers
• We will find out what exactly Dudley saw when he looked at the dementors.
• The reason Voldemort and Harry both didn't die when Voldemort tried to kill Harry, will be revealed. Which JK announced she has never been asked why that has happened. JK has also revealed that the answer to that question (although she hasn't told us) is a very important part of the plot line.
• We will see more of Draco's mother, Narcissa Malfoy, now that Lucius is busy. In jail - busy whatever
• We'll learn more about Harry's scar in the last 2 books.
• Moaning Myrtle will make an appearance again, as will Tonks.
• More about Voldemort's birth will be revealed, thus helping us understand why he is so evil.
• Muggles begin to notice "more and more odd" occurrences in book 6, says JK.
• The wizarding world is really at war in the sixth book.
• Harry will tell his dearest friends about the prophesy after it sinks in to him.
• We will learn more about Harry's relatives, including his grandparents (though JK says they aren't really important to the story)
• We will find out what happened to Sirius's motorbike.
• Book 6 will be shorter than the 5th book (or at least JK's 99% sure, but will not swear on her children's lives)
• There will be no "new" nationalities of children at Hogwarts. Hogwarts is a British school, and JK says that adding foreigners for the sake of it is not in her plans. Also that she introduced the many nationalites that she wanted to the the Qudditich World Cup
• During an interview, when JKR was asked in which Hogwarts room she'd like to be for 1 hour, she said it would be a room in which Harry has been before, but doesn't know its importance. Yet. (this could have happened in book 5, but we're unsure, so it could have been the Room of Requirment or one of the classrooms, or maybe a lot of other places)
• It's very important in the plot that Harry has his mother's eyes, and that her wand was very good for charms.
• During an interview for Kids BBC, Victor Greensteet (reporter) asked Rowling if Harry would have a dragon for a pet. This is what she replied: "You can't tame a dragon, no matter what Hagrid thinks. It's simply impossible. So no. He has more common sense. He MAY have a different pet in the future, but for now, I won't say anything else". (This could have been Buckbeak, but I'm sure we can expect more pets)
• In the same interview for Kids BBC, the reporter asked J. K. if Harry had ever used the internet, and this is what she had to say: "No. They (the Dursleys) won't let him go near Dudley's computer, and Dudley is the only one who has a computer. They hit him if he gets too near to the keyboard. So the answer would be No. I use it a lot, but Harry doesn't. Wizards don't really need to go on the web. They have an even better way to find out what's happening in the outside world, which I think is a lot more fun than the Internet, but I'm going to keep quiet on this one."
• The choice between what's right and what's easy will be a pillar of the plot in Harry's last 2 years at Hogwarts almost a huge Stars Wars epict (I think I have only seen the first two movies)
• Harry's parents' profession will be a big part of the plot. There have been rumours that James was an Auror and Lily used to be before the birth of Harry but it is unsure at the moment.
• Something HUGE will be revealed about Lily Potter.

Book 7

At the moment there is no word on what the title is going to be becasue seriously what do we care we are still waiting for the sixth book to come out!

Facts

• It's Harry's last year at Hogwarts (Duh)
• We'll find out why certain people become ghosts after death.
• A revelation about Lily Potter is made
• Lupin will play a big role
• The last word of the seventh book, according to Rowling, is "scar." She says that she has written the very last chapter already  and that the last chapter contains details of what happens to each surviving character.
• Harry will be in his seventh and final year in book seven. The events of book seven will take place between July 31, 1997 and the end of the school year, which presumably will be June, 1998.
• Harry will turn seventeen on 31 July 1997, and therefore will be of age in the wizarding world and old enough to obtain a license to Apparate. Neville Longbottom will likewise be of age at the end of July 1997. Ron will turn 17 in the sixth book.
• Hermione will turn seventeen in September 1997, and therefore will be of age in the wizarding world and old enough to obtain a license to Apparate. 
• We will learn why some people become ghosts and some don't.
• We will learn something very important about Lily in book seven:
• Interesting things to watch out for, if the usual progression of school life continues:
  • In book seven, two students in Harry's year will be made Head Boy and Head Girl. They will not necessarily be Gryffindors.
  • In book seven, Harry and his classmates will be taking their most difficult set of tests, the NEWTs, and making preparations for their careers in the wizarding world.
  • The last chapter is written. It tells what happens to everyone after the tale is finished (those who survive)
• There is no university after Hogwarts and no further Harry Potter books.

Rumours

• Snape will save Harry.
• Professor Trelawney's first sucessful prediction will be review
• A desparate character manage to learn magic late in life. (The Dursleys)