Here's who I see as shoe-ins:
Geno (absolutely HAS to happen, we already have ridley and krool, complete the trio)
Skull Kid (we're overdue for a new Zelda rep, unique design, potential for fun and interesting fighting style, only Zelda game not yet represented by a character besides SS)
Banjo-Kazooie (in terms of retro reps, this is the best we could possibly get for the n64 era, highly requested, considered for melee, rare and Microsoft are good as gold, it's TIME.
As for echoes:
Ken (ryu's natural clone, too obvious, just add fire effects)
Shadow (again, natural clone to sonic, just add some unique animations and boom)
Isabelle (This one I'm a little iffy about but she makes sense, mascot of ac at this point, again slightly different animations)
I don't see Dixie getting in as she would have been revealed alongside krool
I don't see any indies making it as full fledged fighters
Bandanna Waddle Dee would be cool but he seems more like an assist trophy type character (would LOVE to be proven wrong though)
I have a feeling that we wont see any more pokemon this time around, dunno why to be honest
This game seems like Sakurai's way of giving the fans everything they have been asking for. All of the highest requested fighters are getting in, and I'm very excited