i don't know about snape paying back harrry because i think snape is tooooo proud.and maybe harry and voldemort will die now i haven't heard anyone wih that idea.i mean the battle does not ahve to favor one of them.maybe something can go wrong and harry ends up diein after killing voldemort,maybe from being weak or an injury.there is no sinificance about harry only that he MAY be thet one to kill voldemort.maybe voldemort will kill him and the others seeking to kill voldemort kills him together.or maybe the power of loves prevails and not only harry but harry and ron and herms and the whole order defeats voldemort and the dark forces.you know everyone has showed their courage in someway or another and i think they will help in th defeat in voldemrt and personally i think nevlle will be able to help.(neville isn't as helpless as we think)