Ok, so I've been checking
Mugglenet.com periodically today, and early there was a rumor about Book 6 being titled
Harry Potter and The Pillar of Storge (there's an accent on that "e"
Now apparently that rumor was posted on jkrowling.com, but it wasn't posted by her. So someone hacked into the site and posted it there.
Now there is a new title posted on
JKRowling.com called
Harry Potter and The Half Blood Prince.
Don't know how true these are, but checkout Mugglenet.com and jkrowling.com