We've also found out that JK is expected to update her site really soon.
The rumour started when a Potter fan claimed to have got through a door on the site that is normally tightly closed.
They said that behind that door was a message from JK herself dated 1 July that revealed the title.
There was even a video clip that looked just like the other bits of the site, which at first convinced some people.
But some of the things in that video clip didn't look right to Potter fans.
They said it used some American-style spelling and punctuation, which JK hasn't used when writing on her site before.