Been thinking about characters from companies already represented and others that are not and what I think could be likely for the next game. This is mostly in relation to my MWs but with a more detailed view.
Koei Tecmo - I know Koei Tecmo has been working with Nintendo for a long time but I think I've come to accept that it may not mean much for Hayabusa himself. These collaborations mostly involved either the Fatal Frame games or the Koei Warrior games, so it should be no surprise that what we got in Smash were related to those games instead of Ninja Gaiden. But as for a rep, that's likely going need a push, though Hayabusa seems to be getting that. We'll see in the next game if that's enough.
Arc System Works - I truly believe there won't just be one character from this company. Sol Badguy would be the most obvious rep since Guilty Gear is like their golden child series. He could be either in the base roster or as DLC. Either way, he'd be a hyped character.
Then there's also the River City (which already has spirits in Smash) and Double Dragon characters. I think Kunio and Riki may have more of a chance than Billy and Jimmy. Even though Double Dragon has the name recognition, River City always seemed to be more of a priority for Technos Japan and now for ASW. Plus, River City is the most active beat'em up series in the genre and really popular in Japan. So it wouldn't surprise me if Kunio and Riki make it in where as I think Billy and Jimmy would likely need more of a push for their inclusion. Either way, with the way ASW is promoting both series, there's a good chance that Sol won't be the only ASW character.
I know there are some BlazBlue fans here but it seems like every since Guilty Gear got back in the spotlight, BlazBlue seems like it's taken a backseat, so the chances of Ragna or Jin being playable seems very slim to me at this point. They could get Mii costumes, though.
Microsoft (id Software) - Apart from the Doom Slayer mii costume, id Software seems to get along well with Nintendo (according to them anyway). Sakurai has twice pointed out how DOOM is the father of FPS and Nintendo even made a trailer showing how you can play the whole series on the Switch. Plus, there's also the Switch exclusive cover for the 2016 game. Oh and of course, you could say Mario kind of indirectly led to DOOM's existence. It's the kind of significance that I'm sure Nintendo would be looking for in a series for Smash Bros. If the talks with Nintendo led to the mii costume in Ultimate, then there's a good chance that it could lead to him being playable character in the next.
SEGA (Atlus) - I'm not sure if SEGA has series that are that highly demanded or that obvious. Sonic and Bayonetta were very obvious and Persona had Atlus but I'm not sure what other series have going for them. The only series I can think of is Shin Megami Tensei and that's for the same reason as Persona. However, there's also kind of more to it than that. It's also one of the longest running RPG series in the genre (having started in the mid 80s) and it does feature direct collaborations with Nintendo. Plus, there's also Sakurai's obvious love for RPGs, so this could lead to a playable representation in the game. He and Nintendo would likely want to show where Persona really started from and you can't help but feel that Joker and a SMT rep in Smash feels more complete that way.
Nihon Falcom - For major Japanese companies that don't have anything in Smash so far, this is one I think has a good chance of being represented in the next. Like I said, Sakurai has an obvious love for RPGs. Therefore, it's no surprise that in his YouTube series, he made a video pretty much dedicated to Ys and Dragon Slayer, two pioneers of the RPG genre. Series with that kind of significance is just what Nintendo might want for Smash.