There are so many theories as to who will die, it’s crazy. Voldemort, definitely, but I thought I read that the two that die in the book weren’t part of the original plan, so it’s Voldemort and those two. I don’t think it’d be Harry.
The prophecy in Book Five says that the one will rise to defeat Voldemort is born as the seventh month dies, which could be Harry or Neville. I’d think it’d be awesome if Neville delivered a decisive blow to Voldemort, even maybe the final one, and dies in the attempt. Then, for the rest of his life, Harry wouldn’t be considered the huge hero — it’d be Neville.
But who knows, really. Could it be Snape? Hermione? Ron? Draco? Hagrid? Filch? McShivertits?