Great idea the two of you. Actually, Only last night I was thinking of asking the same question so here's what i think may happen.
1) I don't want Harry to die as it would be too sad so I think at the end, the whole of the magic world will come to a close and vanish. This would leave everybody intact and no chance of another book.
2) I would like to hope that Dumbledore could come back as his 'death' was very strange.
Will leave the rest of you to come up with more info.