I may be rambling and you may be misunderstood because of how badly I express myself.
But in the end, chapter 6 will reveal things that will help us move forward and break the prophecy, and chapter 7 will reveal the connection between Undertale and Deltarune.
Gerson and the prophecy.
So far, chapters 1 through 5 have already been written, ending exactly the same way (except for chapter 5 with the Weird Route) Chapter 6 will demonstrate that the prophecy can be broken, and chapter 7 will show a world that avoids destruction.
With the world destroyed, Sans would escape from Deltarune along with his younger Papyrus and with his knowledge of timelines, they would arrive in Undertale.
At this point, it's not unreasonable to think that Sans comes from Deltarune; this could be confirmed in chapter 7.
@ElromanoffT500@CartoonsOTMoon Los ojos y la boca + ese aspecto de muñeco de tela/plástico da la impresión de ser algo poseído por The Mimic, un endoesqueleto de FNAF que puede imitar cualquier cosa