- A likely canidate for the HPB (title of book 6) is G Gryffindor.
- Director Alfonso Cuaron related, that a graveyard will become important in book 6/7.
- A new MoM will be assigned. We don't know, whether the good or the bad guys will take over the Ministry. Athena suggested, that the position may even stay vacant for a while.
- LV was always the one to make the first move. In PS/SS he tried to improve his situation by getting the stone for himself. In OotP he tried to get the Prophecy. Does he need more things to prepare the war for a new kingdom? Or will the war finally start?
- Many wizard's homes are poorly protected. Will he wage a war against people's homes?
- Will he turn Harry's love interests against him?
- We don't know how muggles, wizards, giants, and other groups will get along in times of war, but this may be needed.
- How effective will the new DADA teacher be? A good one would help.
- It is still a stormy affair between Harry and Snape. This should change before the end of the series.
- Circumstances of LV's birth will be related.
My theory: LV will send someone off to Hogwarts to do something nasty with GG's grave on the school grounds. His fellows will take over the MoM. A civil war among wizards will begin. Other groups - like giants - will have to choose a side. Harrys love interest will be used against him. He will have a lot of trouble to get out of this.
And JKR will have a lot of trouble to meet all these ends.