JK has also hinted that a key plot line for book 6 was suggested in a chapter of Order of the Phoenix. If you want to try and figure it out, then re-read 'Career Advice', the chapter that JK read aloud at the Albert Hall.
Brian says: I have heard that a working title is The Green Flame Torch! Even if this is not the title, supposedly there is a torch with green light that kills anything evil and restores all good forces! Hermione will be made a prefect!
A new subject is introduced in this book that has to do with apparating, disapparating, and flying!
the UHPFC informs us: "I have a friend at Scholastic and the 6th book summarization says that when Hermione is injured in the hospital wing, Ron and Harry go one-on-one with Voldemort."
BOOK 7
It is Harry's last year at Hogwarts!
Harry and Draco may join forces to conquer Voldemort!
The last word of the book will be "scar"!
One classmate may become a teacher, and it is rumored that it will be NEVILLE!
JKR announces that Lupin will play a big role!
We will find out why certain people become ghosts after death.
This is the book where the revelation about Lily Potter is made.
Snape MAY be redeemed- maybe he'll save Harry?
GENERAL
The secret of Harry's wealth will be revealed.
A new broomstick will be introduced in each book. (Book Four had none, but there was no Quidditch.)
The Ravenclaw Ghost will make an appearance! JK stated on a muggle news show that it is called The Grey Lady!
Past Characters will make appearances- Lupin, Aragog, Sirius, Crookshanks, Pettigrew and even the flying car!!!
Prof. Trelawney's 1st successful prediction will be revealed.
A desperate character manages to learn magic late in life.
Future books will be darker, with more deaths...Colin Creevey, perhaps? "A Fan of Harry's Will Die".
Harry...may...be...EXPELLED!
News of Harry's parents/grandparents- and their former jobs- will be announced. This will be important!
Tom Riddle (UHPFC) reports: "The fact that Harry has his mother's eyes will be very important in a future book. As is the fact that her wand was a nice wand for charm work." Harry won't become an animagus.
If you go to the UK Patent Office's trademark search and type in "Harry Potter" you will come up with 3 very interesting marks - Harry Potter and the Alchemist's Cell, Harry Potter and the Pyramids of Furmat, and Harry Potter and the Chariots of Light. Could these possibly be used for future book titles? Note that this site is down from time to time and the previous links may be unavailable.
I think Dumbledore's merely being cautious. Snape is a meanie as Potions teacher. Imagine how much nastier he could be when he's teaching about dark arts (or even how to defend). Or maybe he's just not very good at defending against evil spells?
I think Snape will get to be DADA professor in the seventh book.
"Mr Moony presents his compliments to Professor Snape, and begs him to keep his abnormally large nose out of other people's business." - Remus Lupin (p. 211, PoA)
Remember in JKR's interview, she said Harry would only spend a short time at the Dursleys' in the summer of Book 6? Maybe by "switching houses", she means he'll go live at the Burrow. Whether permanently or temporarily, I'm still thinking about. It would make his everyday life easier, but then again, Dumbledore said he has to stay at the Dursleys' for safety reasons.
Kris Rucker said this in post #3 :
Can only die if the phoenix dies!!! That's really cool... I guess that we shall see. But, that's an awesome thing to put in the book!!!
That reminds me of that movie The Crow.
Won't you go away
and leave me till the time of dying days
stand here by my side
and watch the river flood and pass us by
12-17-2003 11:08 PM
And it reminded me of the same thing 
