This is my guess, in no particular order.
I'm guessing that Steve and CP8 were intended for an E3 reveal, and if the past two E3s were any indication, it seems like they'd end it off with some long-awaited fan favourite. The two big ones that are left seem to be Geno and Isaac (not sure when Waluigi became a popular pick, but I don't think it was as early as those two), and I don't think we'll be getting assist trophy promotions in this DLC. Plus, the timing would match up for the Mario tournament was was announced for "sometime in November or December" (you'd think they could give a specific month, or even have it that weekend) and the Nintendo online open tournament that ends on November 1st. (the last time we had one, Min Min was announced the next day - that one and the upcoming one are the only online open tournaments that we've had, so I'm not sure how reliable that information is, but I wouldn't be surprised if we got an announcement within the first week of November) Smash Ultimate seems to be going out of its way to fulfill as many fan demands as possible (every veteran and most stages returning; hazardless and Battlefield versions of every stage; detailed patch notes; Ridley, K. Rool, and Banjo...), and Geno seems like he'd fit that mindset.
I don't think that the remaining Fighters Pass 2 characters are going to be entirely third party. I feel like Bandanna Dee stands a good chance, given that he's fairly popular in a variety of regions, but Zelda's 35th anniversary is next year, and with Zelda not having a new unique character in Smash for
twenty years by that point, I could see them saving one for the end. Impa seems like a "safe" reveal rather than an exciting or unexpected one, but Nintendo rarely seems to end with the biggest announcements. (Brawl ending with Wolf; Smash 4's base game ending with Duck Hunt; Ultimate's base game ending with Ken/Incineroar; Fighters Pass 1 ending with Byleth...)
With Dante, I feel like it could go either way between him or Monster Hunter, but both series are pretty popular at the moment, and some comments by Hideaki Itsuno and Hideki Kamiya have me feeling optimistic about Dante.
While I think that we should get another Namco-Bandai character by this point, they seem really reluctant to bring in any of their own characters for some reason. (maybe it's because they don't want to seem biased? Though having two of the many third party character being from their company doesn't seem like it would come across that way) Meanwhile, Capcom seems to have no problem with including any of their series in Smash. (plus, it would mean that we'd get Dante vs. Bayonetta, and Kamiya regretted not being able to make that happen in Project X Zone 2)
Then there's Ryu Hayabusa, but he seems like a no-brainer. Koei-Tecmo's got a long history (they seem like the last big Japanese third party company that doesn't have a playable character in Smash), Ninja Gaiden's got history stretching back to the NES days and two wildly different styles of games, and Koei-Tecmo's close enough to Nintendo that they can work on a main Fire Emblem game and a Zelda spin-off that's the official backstory for Breath of the Wild. I'm a little surprised that he didn't make it into the base game, and I'll be confused if he's not in the DLC at all.
I'm not 100% sure about the order, though after Bayonetta, I think they'll realize that action characters will take a lot of time to balance if they're going to emulate the gameplay from their home series, so I don't think they'll save Dante or Ryu Hayabusa for the end. I do think that Geno will come out (or at least will get announced) this year if he does get added, and if we get a Zelda character, I think they won't be out until next year, due to their series' respective 35th anniversaries.