To be honest, if I had to make a wild bet, I think we're getting a Capcom rep (likely Monster Hunter) and a first party. I don't know who that first party will be - I was thinking Octoling, Pearl/Marina, or DJ Octavio, but I do think they would have saved the Callie and Marie costumes if that was the case. I also thought it could be Impa or BOTW Zelda, but with how odd development has been going for BOTW2 plus the Age of Calamity spirit event, I guess that isn't the case either.
I could be totally wrong, of course. I also think Pythra's Mii costumes will tell us a lot, as both Lloyd and the Monster Hunter armors are in danger of returning and with them their chances - and the MonHun outfits returning could also mean no Capcom character in general which knocks out a bunch of frontrunners.
That said, barring any disconfirmations, Monster Hunter fits the idea that this pass has been shoring up representation that was in base game or too late to be added to base. Rathalos is great, the WOL sub-world is great, but especially with Rise coming I can see Nintendo wanting to really hammer home that Monster Hunter is in Smash.
There's also a few tinfoil hat theories that the final character is a last-minute negotiation. Perhaps that means they're from a Switch title that hadn't or hasn't been announced yet. Perhaps it means it's someone whose negotiations took a long while, like Sora for example. Hell, maybe Nintendo saw that Sans blew up the internet and made a final sudden push to make an Undertale character as a playable fighter? We just don't know.
But yeah, playing it safe we get Monster Hunter and a first-party. This means I'll be pushing for my weird and unexpected picks, so let's get Ayumi Tachibana in here for our Visual Novel rep! Or better yet, you'll all be sorry when they announce Style Savvy Switch and add the Stylist like I've been wanting. I will take whips and stones if it means getting one of these fun, unique first-parties in this game.