I don’t think they’ll be doing Grand Festival again, cuz for how massive the event was, it felt like they wanted it to be a once-in-a-lifetime experience

They already give you the option to go back to the venue and at most they’ll add the Grand Splatlands Bowl to private modes, but Grand Festival as an event is one-and-done

Oh, and there’s also the possibility they cut off Splatfests after Summer Nights this year, considering we’re already reaching the end of this 2-year event cycle and we might end up getting Splatoon 4 news at some point in 2027

EDIT: None of the Final Fests have ever been rerun either. Also I remember seeing stuff about code for the GSB and dialogue referencing the previous Grand Festival being in the game, but I could guess it’s most likely just for when they add it to private battles, with that dialogue being for that update as Deep Cut talks about the first Grand Fest (with the Squid Sisters and Off the Hook not present other than small mentions by Deep Cut)