You can go to the official JK Rowling site, she there explicit tore down some rumors, like the sixth book wont be the Green Flame Torch and that neither of the trio is going to be an Animagus, but in an interview she replied to an answer in the following way: " If I were Harry Potter, then I would go and hide somewhere save for the things that are going to come! " or kinda like that ( you can find it on Mugglenet ) and that after the 7 th book we would know everything about the past ( so Lilly and the Marauders ) that there would be no need for an 8th "epilogue" book. Thats what i ve heard.
Ok here's what I know:
The next possible titles are : Harry Potter and the
-Mudblood Revolt
-Quest of the Centuar
-Forest of shadow
-Second War
-Secret of the Veil
-Veil of darkness
-Sealed Chamber
...Not much help, really, seeing there's only 2 more books and 7 possible titles...And THE GREEN FLAME TORCH is NOT a possible title...check out jkrowling.com. 😄
Another thing I read is that someone important dies (everybody knows that) and someone switches houses. (as if!)
Also, Snapes past will be revealed and you'll find out why he left Voldy.
I don't know... If anyone wants to find out more hairbrained theories, check out these links!
http://www.theorderofthephoenix.net/book-6.htm
http://parentingteens.about.com/od/harryp5/a/harry_rumor663.htm