This is my Deltarune plot prediction lock of the century:
The Prophecy ends with one or more heroes having to be erased, with the world changing into one where they never existed: I.e. gonered.
Kris's promise is to become this erased hero, thus creating a world where they were never born, and so their greatest sin, what happened to Dess, will also be erased, saving her life at the cost of their own.
In the end, Susie will be too late to save Kris, and they end up erased, creating this new timeline. However, (You), as a higher being, still persist and still remember everything that happened.
Because (You) haven't forgotten, and because (You) still have Kris's love and compassion within you (your love will become theirs, their love will become yours), you are able to make the Hometowners remember Kris and the love they have for each other.
The finale of Deltarune is getting the Fun Gang back together to rescue Kris and create a real new future worth living in.

>>530192064