Deltarune is a game with a tightly interlocked central mystery that has at least 10 hours to wrap up its plot
Feel like it's worth saying this considering how many people seem to treat Deltarune like it has five minutes left to tie together a story full of disparate plot threads and mysteries. The main plot of Deltarune likely ties into itself without much issue. The plot threads of Dess, the Roaring, the Roaring Conspiracy, Dess's disappearence, The Roaring Knight's motive, the Prophecy, Ralsei's true nature, who the Roaring Knight is, Gaster, Friend, why Kris is working with the knight, all likely tie into one another and answering one can easily lead to a cascade of answers as dominoes begin to fall, as the great prophet Berdly predicted in Chapter 4.
More over, I think these threads are tied close enough to one another that answering them all in quick succession isn't difficult to feel satisfying, especially over the course of two Chapters which might individually be longer than Undertale. Hell, Chapter 7 alone could be a doubled Undertale considering Chapter 5 is nearly as long as a full pacifist play-through of Undertale.
Which is why I feel like the general feeling of unease if not panic that Chapter 6 and 7 can fully tie the story in feels... kind of performative? Like that feeling many fans have is a result of a hyperbolic view of the degree of how disparate the story is and how many true mystery and plot threads there are to be wrapped up, along with generally being miffed about the overall degree in which Chapter 5 advanced the plot, which I understand. Although I believe Chapter 5 does deserve some flowers for not creating any true new plot threads, which was a worst case scenario people feared.
Of course Chapter 5 does deserve some flack of its general slow pace plot development wise following Chapter 4, along with Asgore's vague posting. Had Asgore simply said "The day Dess disappeared" rather than "that day" or "the incident" before getting to his main point about how Asgore's unneeded obsession and self prescribed blame and guilt for the incident would be fine. Pushes forward the narrative a little more without revealing the true nature of the incident which could give the game away for the rest of the mysteries too early along with keeping the focus on its main point; how Asgore treated himself following it and how it was the beginning of a completely self-imposed downfall.
Now focusing back in; me saying the plot can easily wrap up in the course of the final two chapters isn't me saying that Toby Fox is some writing messiah. Rather, it's me looking at what the main plot entails and the understanding of how much game run time is left and seeing that it isn't a herculean task to be overcome for Toby.
Hell, I wouldn't be surprised if Chapter 6, while plot heavy, doesn't actually fully answer many of the actual central plot threads and mysteries. Rather I'd expect Chapter 6 to simply begin crafting the shape in which the answers for things to unravel, while still answering questions about the Holiday Family tragedy, but I also think a lot of fans are jumping the gun how heavy the chapter is going to be tonally. There's going to be a good amount of jokes people, if not a lot. Chapter 6 is likely going to be a lot more like Chapter 4 than a Cormac McCarthy novel, but that's another post for another time lol.