Captain Toad (with Toadette as an alt)- The current rising star of the Mario series, starring in his own game and being prominently featured in many recent Mario games. He may not be able to jump canonically, but Sakurai will surely get creative to work his way around that apparent limitation (some have suggested that he could get gradually lighter when throwing things away from his backpack).
King K. Rool- We know for a fact that the Ballot will most likely be looked to for choosing some characters (
https://mynintendonews.com/2018/04/...be-used-for-reference-for-future-smash-games/). So this is probably the best shot that K. Rool has to make his long-awaited debut in Smash. Thanks to the Mii costume, we know that he's on Sakurai's radar. Plus, the many alisases he went through could give him a vast arsenal of attacks (Cannonballs, Blunderbuss, Helicopter Pack, Boxing Gloves) that would make him stand out from the crowd.
Lycanroc- For many, Decidueye is the bird of choice when it comes to the next Pokémon character in Smash. But as far as character selection in that particular franchise for Smash goes, the dev team usually turns to the characters that are (or are planned to be) prominent in the Pokémon anime. This is what gives the edge to Lycanroc over Decidueye in my opinion, because the former was heavily pushed commercially by TPC, not only in the anime with it being Ash's ace Pokémon, but also in the games, and other forms of merchandise. Its build as a quadruped could also make him really unique in Smash's environment, which is something Sakurai always aims for with character choices.
Alph- Since Smash Switch most likely started as a port, it is safe to assume that the development team turned to unused resources and assets to make additional characters. And since Alph was most likely planned in Sm4sh as a clone, instead of a costume, of Olimar, he probably was an easy character to make for the dev team, being a clone. This furthers the trend of "free dessert" clones that we saw in Smash since Melee, and will likely reoccur here.
Rex and Pyra- With Xenoblade Chronicles 2 having entered development in mid-2014, it is safe to assume that the game was far enough in development by the time Sakurai decided on Smash Switch's roster (based on general consensus, mid-to-late 2016) to turn there instead of X. Furthermore, their unique "affinity" mechanic could easily translate into Smash's environment and would offer a fresh new idea to the roster.
Sheriff- Ever since Melee, there has been a trend of Sakurai adding a "surprise" character that represents a piece of hardware from Nintendo's past (Mr. Game in Watch in Melee, R.O.B. in Brawl and Duck Hunt in Smash 4). So I figured that having a character from Nintendo's arcade days, before any major successes in the gaming industry, would be a bold move that very few people would expect.
Takamaru- There has also been a trend of adding a character from the NES days (Ice Climbers for Melee, Pit for Brawl and Little Mac for Smash 4). Many characters could be brought up for this position, but the one that stands out is Takamaru, who has been heavily considered by Sakurai multiple times beforehand, ultimately not making it in due to his lack of awareness in the West. But his appearance as an assist trophy in Smash 4 and the release of his game on overseas Virtual Console could make the difference for him this time around.
Chorus Kids- There is evidence in Smash 4's data that a Rhythm Heaven character was at some point planned for the game, but cut during development. Reasons for that are unclear (most point to time constraints, which is the most likely), but this means that that franchise is on Sakurai's radar. A rhythm-based fighter is something we don't have in Smash yet, and I think that having the Chorus Kids as a "blank slate" character which incorporates many RH minigames in a Game and Watch-style moveset would best do the series justice.
Inkling- Confirmed.
Rayman- Nintendo and Ubisoft are very close to each other, and this has shown in recent years. From Rayman Legends initially planned as a Wii U exclusive, to Nintendo publishing some of Ubisoft's games in Japan, to Mario and Rabbids and even trophies of Rayman characters in Smash 4. Rayman is a modern gaming icon, being present across all platforms and even on the mobile market, and is pretty much Ubisoft's Mario. Also, his limbless build would make him a truly unique Smash character.
Steve- I may be crazy, but hear me out on this one. Minecraft is a cultural phenomenon (which I don't need to elaborate on). I think that, while this is unlikely, Steve encapsulates all of what Sakurai looks for in a third-party character: significance to gaming and iconicnes: and Steve's pretty much the face of modern gaming. Plus, the entire concept of Minecraft, based on construction and tool crafting, would be interesting to translate in Smash and would make Steve stand out. And as a reminder, since Phil Spencer, head of Xbox, is interested in Banjo-Kazooie being included in Smash, I see no reason for him to turn it down for Steve, especially since he seems satisfied with collaborations made with Nintendo on Minecraft cross-play (
https://gonintendo.com/stories/2929...s-nintendo-on-their-working-relationship-thro).