So, a small write-up on how I perceive Geno's chances. It isn't a huge one, but it's a compilation of everything that has gone on at this point and my final thoughts on the matter at this point in time. Let's see here:
WHAT HELPS GENO'S CHANCES
★ The biggest thing he has going for him is that Sakurai has mentioned him in an interview prior to Ultimate, which I'm sure you are all aware of by now. Firstly, he acknowledges that Geno was 'very popular' in the ballot. Secondly, he stated that he has wanted Geno since Brawl, something that couldn't happen for reasons he has not disclosed. However, he gave us the Mii outfit in Sm4sh (the only one that received a splash screen and a HUGE amount of fanfare, mind) because he wanted the fans to at least feel like he got something. This last bit also hurts Geno's chances, but I won't get ahead of myself here.
★ Super Mario RPG got a Super Mario Kun segment in 2013, showing that he is, at the very least, remembered by both Square and Nintendo. While it was rather belated, likely due to Square's and Nintendo's poor relationship prior, it finally happened.
★ The SNES Classic was released in September and October of 2017 in all regions. Of the 20-summat games included, Super Mario RPG just so happened to be one of them. In May 2018, quite a few months after to promote the SNES Classic and pretty shortly before they stopped its production, Nintendo of America acknowledged SMRPG's anniversary on Twitter with the #TeamMallow and #TeamGeno tweet.
★ Prior to The Game Awards of 2018, an HQ Trivia quiz sponsored by Nintendo appeared for their smartphone mobile app. Super Mario RPG was not only name-dropped, but Geno himself also was, being the focus of a trivia question among ten. Considering this is starting while TGA is getting attention and at the beginning of Ultimate's DLC reveal cycle (given TGA revealed Joker officially), it's a point of interest.
★ Super Mario RPG has been getting multiple references in Smash Ultimate. Piranha Plant's classic mode image references the Super Mario RPG commercial in Japan, whereas Megasmilax, Smilax, and Chewies are mentioned in its guidance. Along with that, Piranha Plant's potted alt references those very few times it ever appeared in a pot, one of which being said commercial. Finally, the cherry on top is the fact that, of all of Square's properties in Smash, the only extra content outside of Cloud's bare necessities are Geno's and Mallow's spirits, Mallow's being an ace and Geno's being a legend. Geno's spirit icon, too, is able to be used as a profile picture in Ultimate.
★ Since the ballot, Square has actually shown that they themselves have not forgotten about SMRPG and Geno either. In their 2017 orchestral album Memoria, showcasing the best of Yoko Shimomura, Beware the Forest's Mushrooms and Goodbye, Geno — the two songs most frequently associated with Geno — were featured. This is also the first time since the original SMRPG OST that SMRPG's music has gotten official album acknowledgement from Square Enix.
★ The fact that most of SMRPG's references have been from after the ballot since SMRPG's release is a very neat point of interest, as a matter of fact.
★ One of the directors of AlphaDream, Chihiro Fujioka, initially stated in 2013 that they weren't sure if they wanted to use Geno and Mallow again because SMRPG 'wrapped up their stories nicely'. However, shortly after, the same director backtracked with another interview, in which he stated that they decided that they'd like to use them in future games, if at all possible, and states that he wonders how they could use them. The fact that he was initially unsure and so quickly changed his mind is very interesting, indeed. Maybe the dude received a lot of backlash, or the rest of the team didn't approve + wanted to see them come back? No one knows.
★ Nintendo of America's treehouse staff has stated that they are 'aware' of the fan base asking for both Waluigi and, of course, Geno, saying that they are listening.
★ Geno's spirit tends to be front-and-center for promotional spirit graphics. He's been featured both on the main menus and Nintendo Direct as Shulk's spirit equip, as well as an appearance in spirit-related news on the Switch as an equipped spirit on four characters versus two Bowsers. It's minor, but it's a point of fascination.
★ PolarPanda's source's superior has gone on record to state that Geno might be DLC. The source has also said that brand-new Mii costumes made for Ultimate in particular (nothing on ported ones, though) are meant as consolation prizes and tend to be in NoA's awareness pretty quickly. This is shortly before NoA listed Mii costumes as being for sale at 75c a pop on their support pages. Either ported Mii costumes are not consolation prizes (and therefore, confirmation that the character will not be considered for Ultimate at the time being) or they are not yet aware of Geno's Mii costume making a return. Either way, for a supervisor to believe that Geno may be DLC, something must be going on that we don't know of. Such a bold rumor doesn't just sprout out of nowhere.
★ Despite Geno's and Mallow's spirits being present and Yoko Shimomura being on the team (whose indie remix albums, unassociated with Square, have had SMRPG remixes all through them, no problem), SMRPG music of ANY kind is not at all present in the game. Along with that, there are no lesser SMRPG spirits alongside Geno and Mallow, despite them likely being easier to license out. The proof of that is in an old 2008 Scholastic's book, featuring Mario in an adventure through old SMRPG locations with a few SMRPG characters even making appearances (the most notable being Frogfucius). If an obscure book can feature those lesser characters and locations, why not Ultimate? Considering music and spirits are important points of challenger packs, this is a point of interest.
★ He's from the Mario series, so despite his age, being from Nintendo's flagship franchise is a huge boost for him.
★ Obviously, he's quite fan-demanded and is definitely a Mario RPG fan favorite.
★ Finally, we have a Nintendo senior artist stating in 2015 that Geno was hot talk in the office. It could easily be because of the Mii costume, though... but it is still interesting.
WHAT HURTS GENO'S CHANCES
✘ Nintendo of America hyped up the Mii costume on their Twitter with great fanfare, saying, "LOOK WHO'S BACK!" verbatim in regards to Geno's outfit. They may well consider the Mii outfit a sufficient 'return' for Geno, which isn't a good look for his chances as a full-fledged fighter.
✘ The obvious elephant in the room here is Square's stinginess. With how little they allowed for Cloud in the base game, the presence of SMRPG material being the only stuff in Ultimate that seems 'extra' could also be a bad sign for Geno. It could be all that they could finagle out of them as a consolation prize. Square could have also easily said 'no' to Shimomura's music in the game, despite evidence pointing at her using those tunes being rather easy. They may also not view Geno as profitable enough to be a playable character, therefore allowing them all rights to deny his inclusion.
✘ If the Mii costume comes back, it may or may not confirm that he has no chance as a playable fighter. However, it could also only confirm he isn't in the Fighter's Pass, which doesn't necessarily bar him from future DLC plans, if any of them happen.
✘ Nintendo could easily choose another, more well-known Square rep, the most likely of those being Erdrick and, to a lesser extent, Sora. That highly lessens Geno's chances for the Fighter's Pass, and we do not know if we will get more fighter DLC beyond the Fighter's Pass at this time.
✘ The biggest obstacle Geno faces is that he is a 20-year-old, one-off side character. While he may be from the big ol' Mario series, this fact undeniably hurts his chances the most. It makes those huge lists of pros he has look like scrap meat under the pressure of this point.
WHAT'S DEBATABLE?
We do not know if the Yoshi's Crafted World Yo'ster Cookies reference is even meant to be a SMRPG nod, and even so, it likely doesn't need Square's OK to be included. We don't know if Geno's Mii costume being ported over would either lessen his chances or completely erase them. We don't know if Smash DLC will go beyond the Fighter's Pass. We don't know if we will get more than one Square rep in the whole DLC cycle (even beyond Fighter's Pass, hypothetically). There is a lot that we just do not know.
HOW IS THE STATE OF THE GENO RIGHT NOW?
His chances are so up in the air that I don't even know what the heck. I'd say, given the Fighter's Pass looks like it'll be a place for big, blow-out characters, his chances are slim for now. If we get more passes with different focuses (like a bigger fan focus) or misc., separate fighter DLC, however, his chances increase significantly again. Given Piranha Plant has its own section with an entire 'individual DLC' segment on NoA's site, misc. fighter DLC is not off the table. Given the site's coding allows for easy implementation of more DLC slots and WoL + character models have extra slots future-proofed in there, it's further proof that it is not out of the realm of question. Sakurai has gone on record to state that the DLC team gets smaller with each character, however. That said, that can still have a lot of nuance behind it. His chances are a solid 10% for the Fighter's Pass in my eyes, abysmally low. If and ONLY if we get further DLC, however, I'd put his chances more at a 40%, which isn't too shabby.