A Weasley has got to die. It's impossible for one not to - there's too many of them! Methinks it might be one of the twins, and Percy will end up coming back and becoming a part of the family again in the time of grief.

Snape may end up teaching Harry how to go up against Voldemort (I'm a bit sceptical, but others have put forward very good arguments as to why he's on the side of good -- Dumbledore and Snape were overheard having an argument in Book 6 "Severus, you must do it!". Why did Dumbledore immobilise Harry in the tower? Obviously so he couldn't fight, but for what reason? So that Snape could do the deed without a fight from Harry?), a few of the characters (Pettigrew, a number of the Weasleys) owe Harry a life debt. I reckon those might come into play, especially Pettigrew's.

Godric's Hollow is a given - something will definitely be found there.

Oh, Krum makes a return, as does Sirius' flying motorbike.

---

On the subject of the films - all three have signed a contract to do #7.