I made a very optimistic roster I'd be glad with:
Unique Fighters (10):
Inkling, Ridley, Simon, King K. Rool: Confirmed
Dillon: Among the other assist trophy absence he seems to be the most likely.
Isaac: Smash Ballot.
Incineroar: Seems like he is the one who gonna be heavily featured in the anime, just like Greninja, Lucario and Mewtwo were last time.
Lloyd: DLC pack 3 mii costume along with Chrom and K. Rool (and flying man but they had an unused 3d model of him so nevermind).
Geno: Smash Ballot.
Jumpman: The surprise character and a retro pick. Every smash has one and I don't think this one will be exeption. And since Takamaru and Sheriff are deconfirmed, Prince Sable is Japan exclusive, Jumpman is one of the last noticiable retro reps.
Echo Fighters (13):
Dark Samus, Daisy, Chrom, Richter: Confirmed
Ninten: Seems really easy to implement and makes a lot of sense. He is Lucas's echo since he does not have a yo-yo.
Isabelle: New face of animal crossing.
Black Knight and Shadow, and Black Shadow: Castle seige absence and assist trophy likely gone. Black Knight was a DLC pack 3 mii costume along with Chrom and K. Rool. And with Dark Samus and Dark Pit it seems we are getting some dark themed echo fighters.
Dixie Kong: Change Diddy's Up-B, give him Tiny Kong's Feather Bow, and ta-da, Dixie.
Ken: Original Echo Fighter.
Celica: Robin without limited magic, just like Lucina is Marth without tipper and Chrom is Roy without the hilt.