book 7   

Dumbledore will come back as Dumbledore the White(the same act that Gandalf did). Snape will be revealed to be Voldemort's son. Dumbledore marries Aunt Petunia. Snape gets angry over this, and therefore Snape kills Dumbledore AGAIN. Finally, it is at last revealed that Harry Potter was not born to James and Lily Potter, but rather was conceived in a one-night stand between Snape and Aunt Petunia. Therefore Dumbledore is Harry's step-father and so is Snape and Uncle Vernon (the former husband). We will also learn that Voldemort is half African American. This spins Harry into a personal crisis in which Harry questions his ethnicity. Harry then has a mental breakdown, starts wearing bling, and adds "izzle" to the end of every sentence.

In few last chapters of book 7, Jesus himself appear as guest character, leading an army of the righteous in a crusade against all magic users, culminating in Harry's execution by hanging. In a postscript, Hogwarts is purified and converted to a megachurch under the pastorship of Rev. Rod Parsley, the hippogrifs are captive-bred for poultry, Hedwig creates a political stir over logging in the Pacific Northwest, and Dobby is relocated to a Malaysian sweatshop.

I agree that Aunt Petunia will have more to reveal - I wonder if she herself is a witch but hates the fact that she is which is why she is so married someone so totally against it. I also wonder if we will find out more about harry's family and he may find a family member that he can actually live with (either that or a wife but he will be a bit young for that). I think the horcruxs will be found early on in the book and the school will reopen and everything will be okay again until after they do their exams when Voldemort will turn up and him and Harry will have a massive duel and Snape will kill Voldemort and save Harry.

I think harry is going to find the horcrux's and destroy voldermort. I also have a feeling he is going to die once he has destroyed voldermort.
I have also read that there is going to be somthing to do with his eyes, some sort of power and that is why characters always say 'you have your mothers eyes' its a power lilly had and now harry has, although i'm not sure what it will be.