Okay this might be a weird thoughts, but what if the line I quoted in the prophecy dealt with Harry and Neville? I mean it is obviously not a coincidence that Neville and Harry both fit the prophecy. Maybe that line deals with it. Maybe the "either" it refers to is not Voldy and Harry as most of expect us to be. I mean after all there are elipses between the lines. I know she was in a trance and all (to explain the gaps in speech) but prophecies can be read wrong. I mean there is a story in Greek Myth about a king who asked the Delphic oracle if he should go to war. She responded by saying that if he did that a great country/nation would fall. Ironically she was not refering to his enemy, but to his own country. The only thing is that I cannnot see Harry for the life of me kill Neville, nor the other way around. UNLESS! Voldy possesses Harry. Remember the rumour about his eyes? Maybe Voldy possesses/polyjuice/transfigures himself as Harry, killing Neville. Maybe my imagination is getting carried away...