wrt the reworks, if this regards visual assets, there are more than two candidates that I can think of: Adam Isgreen talked about re-rigging Orchid and Sadira to not look like absurd barbie dolls; TJ’s and Maya’s animations are often complained about; and obviously people would like to see a visual overhaul for Omen.
If, on the other hand, we’re talking combat design…I don’t know. I’m gonna say things about this, but I don’t really have a lot of deep knowledge on this, and also if there is cast-wide rebalancing coming in preparation for a new season, then maybe none of us are really informed enough to know what the current cast needs going forward.
Glacius and Thunder seem to’ve either been in the “too hard, any little buff might make terribly OP” bucket for a while, and Thunder has seen many revisions to CotS, none of which I think have really taken, so maybe one/both of them? On the other hand, Keits has said he thinks they’re both strong, and people who dropped these characters just haven’t found the right tech or maybe didn’t value their positive matchups highly enough. We’ve also seen better tournament presence from both characters since. I think it’d be unfortunate to significantly alter their combat designs, since I think they are both really compelling as is. Glacius in particular I’m trying to learn, which I would’ve never, ever said about classic Glacius.
If Aganos gets a rework, I’m going to be sad. In particular, if manually scooping chunks gets replaced with a passive mechanic a la Fulgore, it should signify that manual resource management is dead, which would be disappointing. I’m still in the group of people who thinks Fulgore’s manual meter management was more compelling, and felt that the bot that could do all of the KI things (fireball/teleport projectile rushdown, frame trap pressure, footsies, zoning, etc) and more, but had a high execution barrier just by nature of having to do so much to use all his tools in concert, transition between strategies fluidly, and manage his bar, made a Fulgore master as imposing and spectacular as one should be – but also, I get that Fulgore’s rework was secretly just as much about matchup balancing as it was about purported accessibility concerns (he’s still hard to learn, by-the-by). Aganos I’m less attached to, but I think his combat design is cool, and if he isn’t totally viable then I suspect he’s just an uncontroversial buff or so away.
Er, on that note, I’ve more-or-less come to terms with current Fulgore.
Riptor, similarly, only seems to need buffing to become relevant. I’ve come around on her gameplan, and can see a lot of what I liked about classic Riptor in her, so I don’t want a rework so much…but then again, I wouldn’t know what the devs have in mind for her. As an aside, a thing I’d like to see is maybe a much higher-reaching heavy jump rake that can cancel into tailflip or a fireball mid-air, just for nostalgia’s sake? 
Omen is not a no-brainer for me. If he loses randoized rashakukens just because morons ■■■■■■■ and whined and pretended that fighting games are deterministic displays of pure skill, then I think I’m going to puke. The idea of taking what heavy rashakuken serves up and tailoring your offense to it is a thing of beauty as far as I’m concerned. I guess I’m otherwise not attached to anything in particular about his combat design, and if they’re overhauling his creative assets and take it as an opportunity to change up what he does then I could see myself being totally fine with that, but man, there is a freshness and a flow to the way a good Omen executes on their gameplan, and if he loses that… 
The idea of drastically changing Kan-Ra seems insane to me. There are some vapid trolls who say all sorts of stupid and horrible things about him, but he’s an excellent character and seems to be in a solid position currently, and I want to see the top Kan-Ra players (who have worked especially hard to solve this character! Remember when he was stronger and considered low-tier and people complained about the nerfs?) continue to thrive. IG have been good about keeping an eye on him, and I don’t think anything drastic is called for here.
My main, Jago, might conceivably benefit from the KV reductions by getting some better juggles, since his moves tend to blow out very quickly on airborne opponents. I could imagine him receiving subtle buffs (or god forbid, nerfs) in places, but he’s frequently cited as being a strong character in a solid place balance-wise, and I think I’d be very displeased with a rework that had Jago lose anything…but if you’re going to just give him some new tools, despite a sense that he’s already strong? iuno, surprise me, I guess.
Also, as good a time as ever to bring this up: I’ll also be sad if a sweeping change to the game sees forward-traveling unreactables like Jago’s wind kick become unsafe on block. There are competitive players begging the devs for this, and I’ll be ■■■■■■■■■■■■ about it if they actually cave to this notion that lame SF-style footsies are somehow the uncontestable epitome of fighting game play.
Maya and Cinder are similar cases: each gets anemic damage by the traditional means and leans on a specific mechanic to get substantial damage, and each has been complained about for as much. LCD in particular wants Maya to be more of a “normal character” in this regard. This is another one of those cases like manual meter management and randomized projectiles, where I’d be sad to see an entire design space fall out of favour and leave its fan out in the cold; but also, these mechanics not only avoid the combo system, but take a lot of the satisfaction away from simply opening up your opponent because you do no damage, must be a nightmare to balance, and aren’t particularly accessible, so I could see the rationale in moving away from them.
Maya seems well-balanced right now. I suppose giving her normal damage and taking away her dagger ender, but leaving in the other benefits to dagger charging, would make her OP? I don’t like to see excessive use of damage reduction (or worse, health reduction) to balance out character features, so I guess I’d prefer something like this. At the very least it’d make people complain less about not being “rewarded for blocking correctly”, which I think is a silly idea in the first place.
I might’ve heard rumblings that Cinder isn’t all that strong, despite strong showings at the tail end of the big tournament season. As a long-time Cinder fan, I did want him to hit harder, and I didn’t like the idea of burnout all that much, and I wanted trailblazer to have more regular priority, etc – but also, these desires don’t come from a place of rational thought about gameplay balance. Fired-up, on the other hand, is a mechanic that I like a lot, and is easily justified by triple trailblazer alone, so I hope that stays. On a visual note, I also think they should’ve went more towards Iron Man with his stature.
Anyway, I think those are the main, major candidates I can think of. Of the above, if I had to put money on anyone for a mechanical rework, I might actually go for Maya and Cinder. I’m not confident about this, though. If it’s a visual rework, I can’t really narrow it down from the 5 I noted at the top of this post.
I guess there are other, less immediate possibilities. If air doubles happen, I could see Sadira getting rework attention. TJ could be getting his kick doubles back, which might pass for the term “rework”, even if I wouldn’t bat an eyelid if that happened. Lastly, I can’t imagine they’re counting Shago among the two reworks and being secretive about the fact…