Nintendo just
tweeted out a handful of screenshots in a sort of celebration post for Smash Ultimate's one year anniversary, including this one:
A scene of Mario surrounded by all of the DLC characters and also Daisy. People are saying that because there's no readily apparent reason why Daisy would be included along with all the DLC, that she's meant to be a stand-in or hint towards the last Fighters Pass character.
My favorite little bit of apophenia spawned from this picture is that it's meant to be an oblique reference to Doomguy's pet rabbit Daisy, with her peace sign gesture meant to represent bunny ears.