My friend LittleMissLate emailed me a link to this very short one-parter. It reminds me quite a bit of C.S. Lewis' "The Last Battle."
The Last Word by The PresbyteerPost-HBP one shot theorizes on the end to Book 7. Great reunion piece. Very sweet. If JKR were to choose this route, this is the way I'd love to see it played out.