Dave Lull has sent me a link (above) to a Guardian/Press Association report saying that most people believe that Harry is the final Horocrux and hence will have to die to ensure Voldemort dies.
There is no further link or reference in this one-paragraph story. I will venture a prediction that the theory is completely wrong. Harry will not turn out to be a horocrux and he won’t die in the final book. The ending might be bittersweet, but I don’t think it will be a tragedy.
Quite apart from the logical sense of my view, please note that the source for the Guardian/PA story, in the absence of any other information, seems to be William Hill, bookmaker.