My personal belief is that the tier list for Tales characters if we get one is this:
Lloyd = Yuri > Velvet >> Cress = maybe Luke, I dunno >>> Pretty much anybody else. Kratos (regardless of who gets in, but a lock if we get Lloyd), and the guy who's banned from popularity polls like Yuri is would be the most likely Mii Costumes.
Lloyd is the Banjo of the Tales games, Yuri is the Cloud. Both of them would be very good additions, but it's based on whether Sakurai wants to please the Smash Fandom (Lloyd's been desired since Brawl) or the general public (again, Yuri is banned from popularity polls because he kept curbstomping them.). For what it's worth, Lloyd has already been negotiated for in regards to Smash, but Yuri's going to attract more of a new audience, I think. I would rather Lloyd out of anybody I just listed, by a very large gap as I'm not familiar with them on an individual level like Lloyd, but since this isn't Arle I won't throw a hissy fit over Yuri/Velvet's inclusion.
Then we have Velvet, who seems to be pretty popular but more importantly is from the most recent game. She could be the one, too, but I don't quite see her getting in before characters who are more popular, be it with the Smash fandom or in general. I see her as the "Master Chief" to Lloyd's Banjo and Yuri's Steve, except if Steve was much more popular as a person. She's also a girl newcomer, who would be extremely unique compared to Isabelle, the only other "unique" newcomer as dictated numerically, which I could see as a plus.
Cress I put there because he's the original, but can't think of a good reason besides that to put him in over Lloyd, Yuri, or even Velvet. Luke's game is apparently liked pretty well, too? But to be honest, my bubble is exclusively Symphonia, so I might be speaking out of bias (and ignorance) when I say this: I really don't see a reason for him to get in over Yuri or Lloyd, or Velvet. If anybody more versed can explain why the others stand a chance, please do speak up.
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On contrast, I don't think there's a universe where we get a Tekken character who is not Heihachi, nor a Digimon character who is not Agumon. Soul Calibur is more debatable, but I'm pretty sure Nightmare still has a decently sized lead. If there are up-and-coming candidates for Bamco I didn't mention out of ignorance, do tell!