Woah, cool. If true, then...
First Parties deconfirmed by theory:
- Zelda
- Kirby
- F-ZERO
- Fire Emblem
- Yoshi
- Mario
- Pikmin
Already has a Unique Newcomer:
- Splatoon
- Metroid
- Castlevania
- DK
Has no one to add:
- Ice Climber
- Game & Watch
- Warioware (given Ashley's deconfirmed, Wario main series maybe?)
- R.O.B.
- Wii Fit
- Mii
- Duck Hunt
And then there's the third parties, which probably won't have a new unique character. That said, Final Fantasy IS conspicuously absent....
Terra? Chocobo? Please not Noctis...
Thus the ones still in the running are Star Fox, Pokemon, Earthbound, Animal Crossing, Punch-Out, Xenoblade Chronicles, and Kid Icarus
So. Yeah. Supposing this rule is even remotely real....
- I think Star Fox won't have a newcomer. Krystal is literally the best choice for a newcomer. Slippy and Peppy aren't really fit for fighting, and it'd be weird to have a unique Panther or the Chameleon guy before a unique Krystal. Maybe an echo of one of the three already in would work for the latter two though.
- Pokemon. Could be anything, but I'm assuming yes, we WILL get one. Most likely Gen 7. Lycanroc, Tapu Koko, ANY of the three starters,
Tsareena Steenee. Hell, even an Alolan Pokemon trainer (Lillie?). I guess they could do the new Eevee evolution, but would Sakurai have known about it at the time?
- Earthbound... eh. Without Kumatora and any Earthbound/Mother 2 party members left, I really don't know. Ninten seems like a prime Echo material.
- Animal Crossing is, obviously, Isabelle. I think she's the ONLY true hard lock we have given her popularity. Now whether she's an echo or a unique fighter is yet to be seen. But if this rule is true, I think the chances of her being unique go way up. That's she's in Mario Kart is worth something, surely.
- Punch-Out could be anyone from that series, honestly. With the adversary theme, maybe King Hippo?
- Xenoblade Chronicles is obvious- Elma. 2015 is too soon, I think, for Sakurai to have known how much more wildly popular XC2 would be than XC or XCX. I'm not sure if she's a hard lock though- he might see Shulk as enough.
- Kid Icarus is a big one here. Though he was more restrained with Kirby, I think it's still possible Sakurai might show some favoritism to what is essentially one of his babies. With that and the adversaries theme in mind, a unique Medusa or Hades is quite possible. And I'd LOVE Medusa. I suppose Magnus, Amazon Pandora, or Phosphora are possible too, though, and the latter two WOULD fit the adversary theme too.
I do think it's silly we wouldn't get a new Zelda character of any sort when we got Daisy. So maybe Skull Kid could be an echo of someone? But who? Either that or my HOTLY REQUESTED Impa echo of Sheik.
I wouldn't say this counts Geno out either. Given he's owned by Square Enix, he might be counted as a "Super Mario RPG" character rather than a Mario character.
And if he wants to throw Kirby something, hey, Dark Metaknight is right there. But as much as it'd up the chances of some of the girls like Impa, Elma, Isabelle, and Medusa and thus slightly hope it's real.... I do ALSO slightly hope this theory is untrue if only for the chance of having Bandanna Buddy.