According to a tip posted by fan site Godric's Hollow, Harry Potter and the Half-Blood Prince author JK Rowling has signed a release date agreement for the book. But The Leaky Cauldron's contact reports that Rowling "is still writing the book and once she does hand it in there will need to be plenty of time for editing and marketing before it goes on sale."
From Godric's Hollow.net:
"According to my Scholastic source (whom I've been warned not to release his name or I will never receive little tidbits again), Scholastic/Bloomsbury/WB have finally gotten a release date agreement out of J.K. Rowling for Book Six. Due to contractual reasons, there will unfortunately be no formal announcement regarding this fact until they are ready to release the date. However, I have been promised that there has already been printing of what material has gone through the editorial stage. Also, since they have reached an agreement, an announcement is not too far off. Thank you JK! Big applause!"
This is not true. As a trusted source has said, all that's definite is that it will possibly be released next year. JKR is still writing the book (which also puts to rest other rumors that surfaced today about it already going through editing), and once she does hand it in there will need to be plenty of time for editing and marketing before it goes on sale. There is no real, supposed, projected or definite publication date yet (as the lack of one on JKRowling.com would seem to suggest).
Take both as rumors until we receive the official release date of the book, which we will be sure to pass on to everyone.
Update: CBBC Newsround has been in contact with Rowling's agent and they categorically deny all aspects of the Godric's Hollow rumor.