I have not commented on these boards for months. However, with the announcement of additional DLC, I might make a few predictions.
I could see the last fighter pass slot being one of Ryu Hayabusa, Doom Slayer, or a Capcom character (there is a multitude of franchises to which could be selected, Resident Evil, Devil May Cry, Monster Hunter, Ace Attorney being the primary ones).
As to the additional DLC fighters, I think there are going to be three. Call me very conventional, but I think there are two primary reasons why its going to be three.
One is Sakurai's own omission that the development team will be shrinking over the course of the DLC period. I think, after the Fighters Pass wraps up in February, the additional fighters will take much longer to come out, and maybe even until the end of the year to release all three of them. I don't think there will be enough time, budget, and manpower left for another five unique newcomers.
The second, I do think its pretty suspicious the character select screen was re-arranged in a way to which there will be three additional slots left over after the Fighters Pass.
Anyway, as to the additional fighters. My primary prediction is that one of them is definitely going to be Geno. There are two primary reasons for this:
1. Sakurai's own personal preference. I think Sakurai will want to get this out of the way as this is something he still wants to do apparently (2016 was only a few years ago).
2. The omission of the Geno costume. Its pretty odd the costume did not return with Hero's update.
I think Geno is by far the most likely DLC character at this point, and I would be quite surprised if he does not happen.
As for the other two characters. It could be anyone's guess. It could be promotional Nintendo characters (like Corrin was with Smash 4), even more legacy third-party characters, or even promoted Assist Trophies (most likely it would be Waluigi or possibly Isaac). I think the most likely scenario would be possibly characters Sakurai deems to be a particularly big deal (maybe Sora from Kingdom Hears, a Digimon, or even an anime character). This could be uncharted waters.
Also, to dove in to the topic on the "lack of female representation", I always felt a lot of these posters were a disingenuous bunch. A female Smash/Nintendo fan literally lamented to me that Dixie Kong (who is legitimately one of gaming's most notable heroines, and certainly the most legendary heroine Nintendo has outside of Samus), got little support because in the Smash community for female characters, "No A** + No T*** = No Support".
Dixie Kong is legitimately among the biggest characters of her franchise (Donkey Kong). She emerged on the scene before even Lara Croft and Jill Valentine, and both games she co-starred in were among the Top 10 best selling games for the SNES. In Japan alone, DKC3 sold on par with the mega hit Chrono Trigger. Dixie Kong is a legend. She was among the first female characters to star in a mega-hit game and be popular not just for her sex appeal (like most female characters are), but rather, as another female fan put it, "cute, cool, bad***".
Dixie Kong is a character that was/is unashamedly feminine. She was a girly girl and proud of it, and even made cool for it. Her massive ponytail allowed children playing the DKC games to breeze through obstacles far too challenging for them to tackle head on with Diddy and Kiddy, and plus flying/gliding was just plane cool.
Dixie Kong had something called "Mario appeal". She is a character that can be adored and loved across all demographics despite having a very unconventional design. Her appeal as a female character lies outside of merely being sexually attractive or "waifu bait", but rather who she is as a whole. At the same time, Dixie would not be Dixie without her femininity. From her oversized ponytail to her pouting when she got hit to her casually popping a bubble gum bubble to get in the lead from under Kiddy, she had a femininity to her design from physicality to behavior.
She also subverted tropes in a time when it was very unconventional to do so. She still remains the only Kong to never have been kidnapped by K. Rool, and probably the only one to outright insult/sass him (see her dialog with K. Rool in DKC3). Dixie is a character that embraces femininity while simultaneously discharging some of the tropes surrounding females in media (namely women as either an object for the end goal of a quest usually as a result of being kidnapped/held ransom, or merely as a support type character).
Dixie is a character in the vain of Mario in that she is able to appeal to an assortment of demographics without having to be a character that has a conventional design. Who would think a portly middle-aged mustachioed man with a high pitched voice wearing brightly colored overalls would be one of gaming's most endearing characters? The same is said for Dixie. A girly monkey with a ponytail the size of her whole body, that seems to be girly but has an assertive streak to her.
This gif captures a lot of Dixie's appeal. She seems cute and diminutive, but she is someone that is not afraid to fight and do what she wants. Whether its blowing bubble gum bubbles to get Kiddy out of the way, from sassing and insulting K. Rool, to taking DK's Switch for herself to enjoy. Dixie is a character with a lot of personality in the moment, whether its idly sipping a drink (DKC2's idle animation for her), or lapping up honey (her idle animation in the hive stages in DKC2).
There is a tremendous treasure for the next generation of Nintendo fans to champion for Smash Bros. Dixie Kong is really a character on par with the likes of the Nintendo veterans added to Brawl and Ultimate's "big guys" (Ridley and K. Rool). At a time when people are looking to bring forward side characters and retro characters as far as Nintendo characters go, one of the brightest, shiniest pieces of treasure is still there.
DKC2, DKC3, and Tropical Freeze are some of the best platformers ever made, and Dixie was a tremendous part of the memorability of those three titles. She is an endearing note not just on the DK series, but to Nintendo as a whole. The worth to Dixie Kong goes beyond just "we need another female character guys", but rather Dixie is among the few characters whose merits and prestige as a heroine goes beyond the fact that she is female. She is legitimately a Nintendo All-Star.
So for people lamenting about no female characters for DLC, please, please please, give the DKC games I mentioned a chance, and discover why I am singing praises of "girly Diddy". Dixie is a character that has had a profound influence (Dixie's prehensile hair was probably an influence for Shantae's).
There is a female Nintendo character moving forward to champion. And not just that, she is absolutely one of the most notable and important characters to their own franchise (and a major franchise at that) that's still not playable. Her problem exists that people choose to overlook her. Dixie is a character that stands alongside the greats of gaming not just among heroines, but among ALL heroes. She might just very well be the most endearing Kong of the bunch, and arguably the apex of Rare's character creations.
I do not think she will be DLC, but for those who choose to support her, Dixie can be a gift for the future.