https://boards.fireden.net/v/thread/420623896/
All returning characters + 8 brand newcomers and 3 echo fighters.
Newcomers are: Inkling, Ridley, Simon Belmont, Chorus Kids, King K. Rool, Elma from Xenoblade X, Dixie Kong (not a clone, but she has some moves that resemble Dixie, like her tilts) and Ashley.
The echo fighters are Daisy, Dark Samus and Octoling.
No DQ rep and no Sora either. I don't know nothing about DLC though.
Adventure Mode returns but uses extended versions of some stages instead of exclusive field stages. I don't know if that sounds clear enough.
Yes, and it (Adventure Mode) is indeed a sequel to Subspace Emisary, although details about it are very scarce, since apparently there's a debate about whether delay it to include DLC characters in it if they are made (which I guess they will probably be made) or just go with the Brawl formula of going to secret places to unlock characters that don't appear in that mode like Jiggs, Wolf and T. Link.
All stages return sans Miiverse and Hanenbow, for some weird reason.
Yes, there is a story mode.
Classic mode is same as always, but the final boss after Master/Master and Crazy hands isn't Master Core like in Smash 4, but instead, Final Destination. Yep, the stage itself becomes the enemy and has some weird phases and changes.