So I've played the first few battles now. Some notes:
-While this is a sequel in terms of gameplay, the story seems to be a complete reboot (similarly to what Galaxy 2 did), indicated by the fact that Bandana Waddle Dee does not recognize Kirby at the beginning of the game (much like in the original). Whether this means Taranza and Dark Mind will be the villains again, I still do not know.
-Colossal Waddle Dee now wields a spear, and is the second enemy rather than the first (now coming after new enemy Hornhead). The boss is still a complete joke, of course, as his attacks are still ridiculously slow and he still falls asleep on the battlefield.
-The Shrine of Passwords returns. No passwords have been released yet.
-The Shoppe, Gem Apples, the Gem Apple Tree, Heroic Missions, and Vigor all return. The Gem Apple limit has also been increased to 5000 and costs $40 USD total (in comparison, the original was 3000 apple cap and costs $27 USD total).
-Online functionality has been added, alongside a new mechanic known as Stickers that's supposed to notify the other players of how you're feeling in the moment. Local multiplayer also returns.
-Sword Hero is still referred to as such in-game, with "Blade Hero" only being used in the reveal trailer.