Rate these characters chances.
Banjo-Kazooie
Dante
Erdrick
Lloyd Irving
Poochy
Sylux
Banjo-Kazooie: 20% (I don't think we're getting more than one Microsoft rep, and I just can't see characters from a dead franchise being prioritized over others with ongoing or upcoming games like Steve, Master Chief, or even a Battletoad. The fan demand is certainly there. The question is, do Microsoft and Nintendo care enough?)
Dante: 15% (Even though Joker opened the door to other potential newcomers not needing significant Nintendo history, Dante would probably have to be toned down a lot and his moveset might be redundant with Bayonetta already being playable.)
Erdrick: 40% (Dragon Quest is huge in Japan, and even though it's much smaller in the West, adding in a DQ rep that looks like Goku with a sword into one of the biggest crossover games of all time would win over a lot of people and be a great way to make the series bigger in the West. However, Dragon Quest is owned by a lot of different parties and Sora from the Kingdom Hearts series is more popular worldwide.)
Lloyd Irving: 30% (Bandai Namco still only has one rep in Smash despite assisting with development. However, Lloyd faces competition with Heihachi, whom Sakurai originally considered to include in Sm4sh, and Yuri Lowell.)
Poochy: 50% (Poochy is very marketable and would give the Yoshi franchise, which only has one rep despite being part of the "Original 8", a unique quadruped fighter. Only his yarn incarnation has a spirit, and the Yoshi's Woolly World stage from Sm4sh was cut in Ultimate without being replaced with a Yoshi's Crafted World stage. He would certainly be an unexpected pick and help promote one of Nintendo's upcoming games for the Switch. However, if Sm4sh's DLC and Joker are anything to go by, I'm not entirely sure if we'll get any first party newcomers aside from another Fire Emblem character.)
Sylux: 25% (Metroid already got a unique newcomer and an echo newcomer despite being an unpopular series in Japan. I couldn't see it getting another. Although, Nintendo probably doesn't care about "reps" anyways and likely just chose characters based on their own merits. Regardless, we still don't have any news on Metroid Prime 4, and Sylux wouldn't really be a hype-inducing character which could appeal to the masses. Just like Poochy, however, he would definitely be unexpected.)