I just posted the final chapter of the Twin Worlds story on AO3.
It's a short epilogue, with Sara thinking about everything they have achieved, and a problem they still have to solve.
https://archiveofourown.org/works/57662785/chapters/190005926
Yes, there will be a sequel, I've already written a big chunk of it, but I may not post it on AO3.
Also, remember that I will have to delete the story from AO3 before I publish it in November.