I got theories on how the last Harry Potter book will end.

Here goes (coming from someone who has not read ANY of the potter books):

1. Ron gets so fed up with being the one sidelined every single time that he decides to form a plan to overthrow Harry and make Hermione his gf. So he frames Harry, gets Harry into an epic fight, killing him off in the process, kills off Dumbledore who realizes what's happening and cast a love spell on Hermione to make her fall in love with him. Then they live happily ever after.
   
2. Harry Potter finally faces with his nemesis. As he was about to kill him/her, he finds that they are actually his parents. He can't believe it and kept questioning if it was true. Since his love for his parents is so great, he joins the dark side and kills Dumbledore plus anyone who don't agree with him for keeping this secret away from him for so long.
   
3. Harry found out that the dark side isn't so bad afterall. So he organizes a great rebellion to overthrow Hogwarts and place all the teachers which are anti-dark side in prison. His friend Ron and Hermione came to know of his plans and faced him in an epic battle which results in both Ron and Hermione killed.
   

Cheesy endings I know, but would be funny if were to happen.