I'm sure the ballot will have some huge influence on who's gonna be in this game, but I still think certain characters from recent games might have a shot. Though one's definition of "huge" will vary. I don't think we'll have as many newcomers this time around, but I could be wrong. Either way, I'm betting a couple characters will be ballot choices. Or at least they should be, since we've got 90% of the All-Stars and some of the most iconic 3rd Party characters in the video game industry.
Though, for this time around, I'm mostly hoping for Spring-Man, as ARMS' gameplay style would be interesting when going up against the wider variety of Smash characters. In ARMS, there's plenty to separate the fighters as is, but that mostly pertains to mobility and what weapons are their default set. However, no one in Smash plays like an ARMS fighter, and I think, at least mechanically and aesthetically(not that it matters much in a crossover fighting game), Spring-Man makes too much sense.
Other than him, and maybe Buzzwole, Dillon or Elma, there's no one from "recent games" I care too strongly for.
Since the Wii-U era didn't really have a ton of new notable characters, I think some more recent characters would be fine.
Though I'd just be happy with Mega Man and Ryu back.