Unless this is further explained in THBP (which I am only a 1/4 through) The Prophecy says...Either must die at the hand of the other and neither can live while the other survives.
Harry then asks Dumbledore:
"so does that mean that...that one of us has got to kill the other one...in the end?"
So...again if there is something in Half Blood Prince that I'm forgetting, either Harry or Voldemort has to die and I don't think its going to be Harry. Although...I have been known to make mistakes, from time to time