Wolf if he's not already planned prior to the Ballot (But I think he's next after Lucas). Otherwise probably another returning veteran. I really don't know on Newcomers though. But I think even if it's a newcomer it will be at most a Luigified version of a character that's already in the roster (Ex: Dixie for Diddy, Tails for Sonic, Impa for Sheik, etc.). Cause so far DLC characters are a little more simple. Even with Mewtwo they just had to recreate his Melee moveset and just obviously buff it
Though like GP said they didn't say there can only be one. I feel like they could be taking suggestions so they can add characters throughout the next couple of years. For concern about Roster screen space. There was hidden files for arrows at least on the 3DS version that could leave room for a whole new page. (Not that I think DLC will add another 48-50 characters but they still can make room if need be.
King K. Rool- Donkey Kong needed another character and a lot of people wanted him in, so many people were disappointed he didn't get in so he might be it.
Banjo Kazooie-Nintendo recently said they'll allow voting for him, a lot of people wanted him in since Melee, many people were sad he's not Nintendo anymore, but since Nintendo said they'll allow it if he has the most votes...I think more people are gonna look up to him.
how can people see what the votes are?? (adding on to this, i wonder if it takes all the versions of the poll into consideration or just the us one...)
also that image looks different to what i saw before. theres some additional characters so maybe its just a newer version, idk
interesting how karate joe has more votes than chorus kids
also are the third-party characters in order as well because i find it really hard to believe that banjo-kazooie is in last