I'd love Elma. Monolith made her act a bit weird but still XCX is an underrated experience. Albeit Sakurai could have also used that figure for Ray, it looks pretty much like him.
Something else I'd like to throw in here; I was wondering who could be our retro character rep this time. The last three times, they were forgotten NES heroes (Ice Climbers, Pit, Duck Hunt; even R.O.B.) and there were also other characters considered of those who are known are solely NES characters (like Mach Rider or Bubbles) or the Disk System (Ayumi) respectively. Those who were included though, were pretty popular and sold several millions. Looking back now, we have not many options left. We have characters that were only in games/systems released exclusively in Japan which means too little popularity to Sakurai (Prince Sablé, Ayumi, Diskun, Donbe, Lip; also Tamagon whose game did not come to NA due religious issues), characters which aren't very popular (Muddy Mole, Urban Champion) and Foreman Spike, who is basically a Mario character and also probably either Wario or most likely Waluigi.
This leaves us with 6 options:
Sheriff (he's an assist trophy, therefore he wouldn't be much of a surprise or a revival)
Mach Rider (F-Zero is its spiritual successor, and he/she seems to be pretty similar to Falcon)
Bubbles (Clu Clu Land didn't sell that well and she's actually limited in her movement)
Balloon Fighter / Alice (no hope if they don't change Villagers recovery; otherwise they would be the most likely imo)
Mike Jones (his 2 games weren't released in Japan despite the first being successful)
Takamaru (obviously the most likely and most wanted; still we don't know if Sakurai changed his mind cause Takamaru is a pretty popular character nowadays and probably the most known alongside Balloon Fighter).
tl;dr the only ones I think stand a good chance for being the retro rep are Balloon Fighter, Mike Jones and Takamaru.
Didn't include Excitebiker because he doesn't fit in that category thanks to the WiiWare game from 2009.