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?"
Dumbledore says:
"Yes"
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