Oh boy, another poor fool who believes Spirits deconfirm.
First off, welcome to the thread, despite it being the Geno Support Thread and your second post is HERE saying you don't think Geno has a chance. Probably could have said that in the general thread where people would agree with you because they lack the proper knowledge and critical thinking.
So, now that I have the pleasantries out of the way, let me proceed to tell you why you are wrong.
Spirits are nothing more than glorified trophies...and that is saying a lot since trophies where these really detailed 3D models and these are just copy/pasta'd JPGs and PNGs, but they do offer gameplay options while trophies were just nice to look at occasionally so they do offer a smidge more. That said, Sakurai has stated himself on multiple occasions (including the Nov 1 Direct in 2018) that Spirits are a replacement for trophies designed as a system to incorporate more characters, including some that can clearly never be fighters (like Ness's Dad being a phone, or character from franchises long since forgotten, or Pokemon that simply don''t bring enough to be playable nor in a Pokeball) but not every Spirit can't be a possible fighter down the line just because they were a Spirit in the base game.
A lot of people were using this argument because characters in the first Fighter's Pass (all of them now, but only 1-3 at the time of these discussions initially) were all characters that didn't have Spirits in the base game already. Byleth is a technicality on this one because we did have Fire Emblem spirits in the base game but Byleth brought only Fire Emblem: Tres Casas content which means that even though TECHNICALLY SPEAKING we have a fighter that is already from a series represented in the base game in both character and Spirit form Byleth and the Spirits with her are also content that technically WASN'T in the base game due to it all being Trois Maisons content. Regardless, I think this is still a huge deal for characters that a Spirits in the base game but it's been mostly skipped over so let us continue on.
Now I've seen your argument that 'If Vol 2 is like Vol 1, Spirits can't be fighters' which is semi-debunked by Byleth already but also...that is a major 'What If' statement. We have no reason to believe that Vol 2 will play out the same way as Vol 1 other than a getting the same amount of content as before. Sakurai has been doing nothing but breaking rules both he and the fans have set since Ultimate was revealed back in March so I really don't think a 'But what if it's the same?' argument stands strong here.
Now others have said this, but let me add my slight spin on it: Make in the world makes you think that Sakurai, the madlad that he is, would let a .jpg/png stop him from putting a character in the game as playable? That's right: nothing at all! Thus, the idea that a Spirit cannot be made playable as long as future content exists is just plain silly!
Also, I ask you to keep in mind that the Spirits team had very little input from Sakurai at all. He occasionally came in and made comments or recommendations, but he mostly just let them do their thing, which is even more of a reason to let have Sakurai limit himself to putting a character in the game due to have an image of them in the game. That would be like having a sticker of a cake that smells like a cake that someone else put in your oven and you decided you can no longer make a cake because of that sticker in your oven. It's a dumb arbitrary rule that makes no sense at all.
Now to poke another hole into your logic, we've actually already seen changes made to both Spirits and Spirit Battles. The changes were made to some LoZ spirits when Drei Hauser spirits with the same name joined the roster to make sure there was no coding confusion for the game. This is proof that if a character that is already a Spirit becomes playable and thus has a Fighter Spirit, if need be, changes can be made. Also, the Cuphead Spirit Battles changes based on whether or not you have purchased the Cuphead Costume DLC. If you haven't, you battle against Megaman of the appropriate color; if you have, you fight against Mii Gunner int he Cuphead costume with Floral Fury playing in the background. This means that it is easy for them to make changes to long-standing Spirit Battles when new content emerges, like new costumes or Fighters.
Now I saw you mentioned patterns, and the only pattern I can think of that supports you is the fact that all the Vol 1 characters had no Spirits in the base game (barring the technicality on Byleth). Well, I've also noticed patterns with Ultimate, and let me tell you that they trump this one by far. The biggest one is this: Ultimate has granted more long-requested characters than any other Smash game in the series, backed up by the pattern of getting characters like Ridley, King K Rool, Simon, Chrom, Dark Samus, Daisy, Hero and Banjo and Kazooie on top of bringing back all the old favorites from previous titles. This leads into the next pattern, which is that Ultimate has made a pattern of breaking rules both set by Sakurai and by fans. Ridley too big? Nope! King K Rool too forgotten? Nope! Konami sucks and hates Castlevania? Gets two characters! Banjo and Kazooie are a dead franchise and owned by a big competitor? Guh-HUH! Sakurai hates the competitive scene? Training mode and balances changes using competitive player's data and feedback! They will have to make character cuts? EVERYONE IS HERE! Fighter's Pass is the last of the DLC? VOL 2 ELECTRIC BOOGALOO! Fighter's Pass will be all Third Party? Hi, my name is Nintendo, have we met? Fire Emblem can't get more characters? Here is something to believe in!
Do you see this pattern? Sakurai and his team are all about breaking fan rules, and yet here you are spouting about a fan rule, and in fact one of the weakest ones! Also Sakurai has consistently shown himself to be in touch with what the fans are asking about and talking about, to the point of swatting Western fans on the wrist when they overstep and get crazy on any small thing he says. Let me hit you up with one more pattern, one I like to all the Geno Makes Haters Head's Whirl.
Geno fits into every one of these little bits here. He is one of the final long-term requests that have been around since just before Brawl and Sakurai has acknowledge the passion and support of the Geno fanbase and even has stated HE HIMSELF wanted Geno in since Brawl. Geno's costume has yet to return, he hasn't been turned into an Assist Trophy, and yet Sakurai is going to stop his wild ride of breaking rules and pleasing fans all because of an image in his game? Psssh!
Now I've been reading your follow up posts, and you seem like you may be trying to put up a wall. 'It's my opinion' or 'I'm just skeptical' won't work with me, my dude. It's fine to be skeptical, but when facts are lined up and delivered to you and you refuse to accept those facts, you aren't being skeptical: you are in denial. I'm curious to see what you have to say after you read this. If you truly read this and understand what has been said and take this to heart, it shouldn't be that hard to admit that Spirits Deconfirm hold no weight in general, and certainly not against Geno.
If you choose to believe in it after reading this, then you are denying overwhelming factual evidence that trumps what you have in order to maintain your position...and I think that's all we will need to know if that is the case.