I think the end will be a new world a lot like this one, but with magic openly practiced and the supernatural public knowledge. Where Harry won't be the only wizard in the book.
I think things will break at the end of the case files, be very bad and apocalyptic during the big apocalyptic trilogy (it's in the name, so), and then just starting to rebuild at the end in the epilogue.
I'm also currently intrigued with the idea that, with numerous starborn running around, one other than Harry might play the big role that decides things at the end of the case files. He might be the starborn that rights the ship, but another might sink it to actually cause the BAT.
I'd say two thirds into the last book rather than the epilogue as there will be a lot to wrap up I imagine, but we'll see.
But I agree about the timing of the first apocalypse. Likely a cliff hanger in the final book of the case files, leaving us all jonesing for the BAT.
Oh yeah, that would be intriguing. I'd say it was Elaine if anyone...but Listen could be just as good a possibility. Maybe even another one. I'm still wondering about Lara's new head of security. Listen is fairly confident there is hardly any left, but I'd say there was more than just Harry and Listen and Elaine. 5-10 seems about right.
Sounds like a good idea for the new world. Alternatively, it's one without magic at all. But I would prefer one with magic practiced openly. I suspect by the end there will be so few people it will just be small communities rebuilding around the world. Little towns type of thing, but with modern tech and magic, and very small government.