The Chrono series has been abandoned for literal decades, so yeah I don't really expect Crono to get anything.
I don't think Crono will get in, but this isn't really a valid point. Banjo proves that "dead" series can still get into Smash. The last big Chrono Trigger release was Chrono Trigger DS which came with new content, it released in 2008. The last big B-K release was Nuts and Bolts which also released in 2008. Obviously, one of them is essentially an expanded port, while the other is a brand new game; but no one really like Nuts and Bolts sooo...
What really kills the chance of Crono is the fact that we already have Hero fulfilling a lot of the same rolls, in a lot of ways. Now he could definitely be unique, but it does hurt his chances a ton imo. The best I could see him getting is maybe a mii costume or an upgraded costume. I would be surprised if he gets in before Geno because of this.
In my opinion, these are the most obvious potential picks for the Square Enix rep (in no particular order):
Geno: Duh. There's a good amount of evidence for him; but I wouldn't really call him anywhere near guaranteed. If I was giving a % answer, I would say around 40% of him getting in as the next Square rep.
Tifa: Comes from one of the most iconic games in history. Square's next "big" title, and I doubt Nintendo would be opposed to it unless Square still isn't open to music. The music situation for OG FF7 is due to copyright issues, but I don't know if FF7R would have the same problems. I would say she has around a 30% chance of being the next Square rep.
Sephiroth: Same as above, and on of that is one of the most iconic villains in gaming. His moveset would be tricky to adapt due to his rather large katana, but that doesn't mean it's impossible. Regardless, both Geno and Tifa have "simplicity" backing them up. I would say he has a 15% chance of being the next Square rep.
Aside from unconfirmed leaks, all Geno and another FF rep share the same evidence. For Geno, the Geno mii costume did not show up when it made sense to. For FF, the Chocobo mii costume did not show up when it made sense too. There is more unconfirmed leaks pointing towards Geno, but again nothing about those leaks is nearly "definitive" yet. And even then, those unconfirmed leaks mostly just "hint" at Geno rather then explicity stating that he's in.
Another Square rep: In my opinion the "other" square reps I could see happening are Lara Croft, 2B, Neku Sakuraba, and maybe a Bravely character.
Lara Croft is pretty obvious, she is one of, if not the most iconic woman in gaming. Sure, she's more of a playstation icon; but so is Cloud so I don't see why it would stop her.
2B again is a fan-favorite and is also really popular, Square really loves putting her in collabs and Sakurai also likes Yoko Taro's works. The thing that hurts her chances is that she has even less of a "nintendo connection" then Lara Croft.
Neku Sakuraba has the biggest "nintendo connection" here outside of Geno; but he doesn't have Geno's Smash Notoriety or everyone else's general notoriety. That said, there was a leak by Tansut stating that more TWEWY content is coming for the Switch this year, and obviously that content was not shown in the March Direct; leaving the E3 direct and September direct as the last potential places for it to show up this year. Much like DQ 11S, Nintendo helped publish TWEWY Remix outside of Japan; and on top of that TWEWY Remix didn't really do well enough for Square to really greenlight another game by themselves. Perhaps Nintendo is helping publish this new TWEWY content again, which indirectly increases Neku's chances for Smash. He also didn't do THAT bad in pre-release fan polls, as little as they mean.
Also I guess a Bravely rep is possible, considering that that's Square's main franchise for Nintendo; and the development studio for those games seem really close to Nintendo. I think Nintendo also helps publish these games, but I'm not a 100% sure. BD 2 is also a big release for the Switch this year.
Regardless all these final characters make up the last 15% of Square characters that could potentially get into Smash.
So in short, I think Geno has the best shot of getting in as any INDIVIDUAL Square Enix character. However, I think collectively there is a solid shot of another Square Enix character making it in, depending on who Nintendo and Square end up feeling like putting in.