A few things I think should be considered:
1) Since that Famitsu column where Sakurai pointed out the struggles of making distanced development for Smash, where he mentioned "working with publishers". Awhile back, I went over the difference between publisher and developer, and how the term itself has meaning within the context. There were a few important sentences.
Long distance trips have been especially difficult to put together. For example, my trips to Nintendo in Kyoto. Trips to other companies have been problematic, too. Planning new fighters, presenting to publishers, and having meetings have all been indefinitely postponed.
A few things to note...Nintendo is mentioned separately from "publishers". Developers like Intelligent Systems or GameFreak are not considered publishers, but larger companies like Namco, Capcom, or Square Enix
are (think of the meeting for Hero). There are plenty of publishers, so this isn't specifically those 3 companies, but it should be noted that, at the very least, we're looking at
at least 2 publishers that
aren't Nintendo, ergo, there's likely at least 2 3rd parties. I would say it's more likely that it's 50/50 3:3, though I don't have anything to base that on. It's a feeling I have, and that's subject to change in either direction if assist trophy/mii costumes are on the table for "upgrades" or legitimately off the table. (It can be argued that linguistic differences mean that "publishers" may not be indicate a certain amount of companies involved, though I believe that the context suggests it's not a totally unfair assessment. This may simply be up to personal opinion)
2) I think that it's highly likely that a new company will be included in Smash by the time we get Challenger Pack 11. This doesn't really narrow anything down, but I think, if it's a Japanese gaming company, companies like Koei Tecmo or ArcSystemWorks are in the mix. However, I would also argue that any company with a playable character in that isn't from SNK is on the table as well. It seems reasonable to me to expect AT LEAST one character from a new company, and AT LEAST one character from a company already collaborating.
Atlus seems to be SMT3/5 or bust. SNK is most likely out given the wide berth the Terry pack covered. Namco has Pac-Man and Tekken covered, with Tales unaccounted for. To my knowledge, there appears to be a drop off of popularity after that, thought that doesn't disconfirm Namco by any means. Capcom and Square Enix both have substantial backlogs with untapped potential, so I wouldn't be surprised to get a character from either company (though I doubt more than one from any given company, aside from Nintendo for obvious reasons).
3) Each "Season" of Smash DLC has included at least ONE "marketing" pick as defined by the fanbase. Corrin was first, Byleth 2nd, and now Volume 2 has started with Min Min who seems further away from a "marketing" pick from the previous two, though she could arguably still be considered one. Therefore, it's possible that we could still get a "marketing" pick from Nintendo, which I
could see being from Pokemon. I have to agree that games that are still unannounced may not be in a great spot to get a playable character at this point, though it's tough to say that for sure.
Characters I could see from each company, to make things more concrete:
Atlus: SMTV protagonist, Demi-fiend
SEGA- Kiryu, Arle
Capcom- Dante, Amaterasu, Monster Hunter, Phoenix Wright
Namco- Lloyd Irving/Yuri Lowell, Soul Calibur, Dark Souls
Square Enix- 2B, Bravely Default, Neku Sakuraba, Geno, Lara Croft. A lot to go around here
Microsoft- Master Chief, Steve Minecraft
SNK- oof
Koei Tecmo- Ryu Hayabusa seems like their Terry, though I guess I can't rule out others
ArcSystemWorks- S(c)ol Badguy, Ragna the Bloodedgelord
Ubisoft- highly questionable based on content they already have, but Rayman probably. One would think Assassin's Creed and Rabbids costumes would come with Rayman, no?
Activision- Crash Bandicoot
Falcom- Trails in the Sky (funny acronym lmao amirite), Ys to name a few series
What do you think?