Kamigawa and Kara-Tur are very, very different things in the details and execution.
Kara-Tur is pretty much exemplary of the laziest and least effective kind of "Asia-themed" setting, in which it's a big morass of poorly-researched takes on "Asian" in a bland and broad way, with a lot of stuff jammed together. It's not "hateful", but it's just... crap and representative of an unfortunate take on "Asian" culture that was once common.
Whereas Kamigawa is a fairly tight and specific thing, focused on Japanese culture and mythology (specifically) and with a cyberpunk theme.
It's a serious mistake to see them as similar. It is possible that WotC could redo Kara-Tur to be less, well, bad and lazy, but the question is, would it be worth it? Would it be more successful and popular than a Kamigawa setting-book? I suspect not, because Kamigawa could add a whole bunch of cyberpunk stuff to D&D for those who wanted it.
On Toril in general, I think there are really only two ways from the FR to go forwards from where it is:
1) The cautious option, where there is maybe a broader FR book than now in terms of the "core realms", but Maztica, Zakhara, Kara-Tur etc. are still not detailed in any meaningful way. This would probably be the safest thing to do, but even that isn't without risk, because people will ask questions about why they aren't covered. I'm not sure it would achieve much but I suspect it would be popular and it could update SCAG mechanical material to the DND2024 standard (Tieflings etc).
2) The "new edition, new FR" option. WotC have already expressed the opinion that they are not bound by previous canon, and honestly, they could go with a new FR book that was more "full-on", and "rebooted" Maztica, Zakhara, and Kara-Tur. Maztica must be rebooted to be used. You cannot light-touch retcon your way out of the what the original Maztica books did. That just has to go - I think if you did go retcon instead of just pretending it never happened, you'd want to say something which amounted to "Oh the 2E stuff was nonsense written by an invader", and go from there, not even using that material. Zakhara isn't in that bad a state, imho, so it could be more light-touch and just putting a solidly positive spin on it. Kara-Tur needs a rewrite for somewhat different reasons to Maztica. You'd need a pretty big book to be even mildly respectful of them though.
I suspect the first is a lot more likely than the second. If it wasn't for the multimedia strategy I'd kind of suspect they were going to move away from the FR generally, but given we have a movie, possibly one or more TV shows, BG3 (i.e. a pretty big-deal AAA CRPG), and likely other games on the way, likely landing in 2022 and 2023, so just before the 2024 new edition, I don't think a move away from the FR is terribly likely. I do think they're going to update it though. Especially as they have the excuse of the new edition.
As a total aside, on a certain level, the Moonshae Isles (i.e. The British Isles and Scandinavia - or rather just the "colourful" bits of those to a 1980s American eye) are almost as bad as Kara-Tur (not Maztica though, that's a whole other level of "yikes"). They're an example of a very similar cultural phenomenon (Celtomania instead of Orientalism), but they were at least done by people who have a background with those countries/cultures, and whilst kinda gross, at least can't really be said to be racist, just incredibly dumb (they're also more forgivable because they're a much smaller part of the world). If I was passing through I'd probably get rid of the word Ffolk though, esp. as it's a Germanic-derived word given a hilariously idiotic cod-Welsh spin (is there even a quasi-Germany in the FR btw? I actually can't think of one of the top of my head).