Okay, If they aren't turned in KFW (Kentucky Fried Witch/Warlock - see other HP thread) - without having seen the book:-
Harry potter & Valdemort neutralise each other and, if not dead, cease to be 'magical'
Percy 'comes back to the fold' (from the ministry) and gets offed.
Weasly twins killed off
Agree that Lupin & Tonks get topped
Snape turns out to be a 'Double Agent' and is responsible for saving either HP or Hermione, dying in the process
Malfoy Jr and his oppos die (possobly at hands of Death Eaters), Malfoy Sr turns on Valdemort and is either killed or is captured by the 'potter' team and ends up in the nick, grieving for a lost child
Hermione and Ron end up as a couple.
Hagrid and the Giant bint from the French School provide a magical animal cavalry and end up running a magical safari park somwhere.

And I end up pulling all sorts of rubbish out of thin air to pad out this (particularly pointless) post ;-).