unpopular opinion -
I came to the conclusion that Terry was planning to end their story this way from the initial conception of the book. that's why in the book it says the world is 6000 years old and dinosaurs are not real, and everyone is wrong about the history of the world, etc. i think he already knew that the "old universe" will be destroyed and therefore IS only 6000 years old. He knew A+C will create a new, better [aka our] Universe without any supernatural powers influencing it.
I read about his personality and spiritual beliefs- he was an atheist and strongly believed in the idea of human free will. A lot of his discworld books focus on the ridiculousness of people/beings/universes being pawns in basically a big board game between fate, death, and other big "powers," which they are playing out of boredom, or ego-driven to prove a point.
That said, I think Terry would have done a much better job of telling this story and bringing A & C to this conclusion.
