I beat Deltarune chapter 2. It was a lot of fun, the shifts in gameplay were neat, and apparently, it's entirely possible to change the story at some point? Not entirely sure about that one, but apparently, it has to do with Noelle freezing enemies.
As for the ending of the game, I'm not sure whether Kris is summoning a dark fountain in a misguided attempt at bringing Ralsei, Lancer, etc. into the real world, if it's because Kris is really the Roaring Knight, or if Kris is something worse.
The post-game mentions that a carnival is coming up - not sure if that will be in the next episode, or the seventh/final one. (I could see Asriel coming home from university for the carnival, and then everything going horribly wrong one way or another) Also, I'm assuming that Noelle's mother is going to be a plot point later - talking with Rudy in the hospital has him imply that she's abusive towards Noelle somehow, and when Rudy's home, he usually stops that from happening, unless I misinterpreted that conversation.
There seem to be little bits of potential plot points sprinkled throughout the game; it's implied that Noelle has an older sister named December who's likely dead, or at least not in a good situation since even Susie reacts to Noelle's sister being mentioned.
I'm glad to see that they added a feature to make sparing enemies worthwhile - in the previous game, the whole "spare/kill" dynamic felt a little pointless compared to Undertale.