New here, but I'd like to speculate on the Square rep. My personal opinion is that Yuna from Final Fantasy X could be a possibility. While she may be another FF rep, she's a well-known character both in Japan and the West (FF X was super popular), would have a cool moveset, and could be used to market the FF ports that will be coming to the Switch sometime next year. You could argue "Well why not Tidus?" Well, **** Tidus. We already have a blond, sword-wielding FF protag. Give me something else.
As for other DLC characters, I'm of the opinion that they will mostly be third party since Smash 4's unique fighter DLC was mostly third party. Mewtwo, Lucas, and Roy were old fighters.
If I were to guess, I'd say: Banjo-Kazooie (I'm living in denial of Steve, okay), Catalina, Yuna, Lloyd Irving (Bamco hasn't gotten their dues yet), and a 1st party. I'd like to say Rex and Pyra if the costume doesn't deconfirm them. Otherwise, idk, Elma or new FE girl. I want Shantae so bad but I know she's out of the running.