I have absolutely no idea if this list is real or not, but if this is the final list of DLCs, then:
Joker (Persona 5): Completely uninterested.
Erdrick (Dragon Quest): Completely uninterested, though I like medieval fantasy themes more so I'd prefer this one over Joker.
Doomslayer (DOOM): I care even less than Joker.
Hayabusa (Ninja Gaiden): Not a big fan of the franchise, though I played the NES title and I enjoyed it a bit. Interested but not that much.
Steve (Minecraft): I played Minecraft a bit in the past, and I think that the concept of a world made of blocks that you can interact with is very cool. Though, the game becomes very repetitive early, and aside of liking the base concept, I'm not really into the gameplay. Though, Steve may come out as an unconventional fighter, depending on how they implement the crafting and the creation of blocks in his moveset, so I'm a bit interested (but still not that much).
At the end, Piranha Plant would be the DLC fighter I like the most; Since I won't get it for free because I don't even have a Switch yet, I think that I'll buy it when I will get the game (if I will get it), and I'll probably skip every other fighter since I'm not really that much interested in them... the only one I may consider is Steve, depending on how much creative and unique his gameplay turns out to be.
At the very end, the only characters I'm interested in playing as, including base roster, are the Inklings, mainly for the paint/ink gimmick; and Piranha Plant.
Well, at least they brought back Young Link (my favorite version of Link) even though he's still a clone, and they improved Zelda's design (she's not a dark witch from some fantasy movie inspired by the Lord of the Rings anymore, she's finally the actual Princess Zelda).
Still a pretty disappointing character selection overall, and the more they add 3rd parties, the more I lose interest in the Smash series completely.