I'm still curious to learn if the salt mine will even be a significant presence in the interior scenes. As much as they talk it up in the marketing, its presence in both the art and models seems close to nonexistent. Even the exterior of the mountain is still largely themed to a bayou. And while there are some scattered "farm" related props, nothing looks like a salt mine. Makes me wonder if it's just going to be some minor references in the queue.
It is abundantly safe to assume the otter at least will be in the ride as a proper AA. It has been in both of the pieces of art for the ride as well as the detailed D23 diagram. I also know that they've already constructed multiple other minor critter AA's as well.
The project isn't changing fast at present. They've have had a final plan and budget figured out for quite a while now. And unlike with other projects, there's good reason to hope that the budget won't be cut. The executive leadership quickly came to the realization early in development that if they mess this up, there will be hell to pay. If it fails to deliver though, IMO it won't be a lack of budget (and probably not even a lack of decent animatronics), but because the creative team couldn't create quality scenes or a good story/music. Like I said, whatever other failures the ride may have, I actually don't think the animatronics will end up being one of them for a change.
I was/am skeptical that they'll make the target. But that's admittedly purely a feelings over facts thing on my part. Not that there isn't reason to doubt it'll be done by then given their track record. But unlike a lot of the other projects they announce with obvious and intentionally BS dates attached, Disney IS legitimately confident that they can get it done by late 2024. The ride track isn't being altered (even Frozen received a minor alteration to its track near the start that necessitated some significant concrete work). They haven't been dragging their feet either. Significant progress has been made on construction of props and animatronics long before Splash closed.
A lot of the initial work though probably won't look like they're making significant progress because the ride needs to undergo a lot of maintenance and prep to get it ready for the new content. Infrastructure work essentially. So I wouldn't be surprised if we don't see a ton of obvious changes to the mountain for perhaps the first 6-12 months. That's just my assumption though.