Hadn't JK said she'd written the last chapter years ago, perhaps when writing the first book? Since that would be the epilog she'd meant those who survived to do so back when her first printings were for 500 copies, not 12 million. She just had to figure out how to get there. That also might explain the sparseness of the epilog, as a whole lot of details we now consider important hadn't been imagined yet.
Precisely. I would have liked to have seen her original epilogue published either as an appendix (with a note explaining its history) or on her web site, but not as the 'official' ending for the story. I would have much rather seen Ms. Rowling add some more details to the epilogue based upon the characters, plotlines, and concepts which she invented after she initially wrote it.