There is no way Disney would back out of a retheme of Splash Mountain in California or Orlando. If it was ever discovered that Disney was considering backing out of the retheme in the United States, the media would tear the Disney company apart. I understand people who love the ride as is may be in the denial phase in the stages of grief, but the retheme will happen.
I wouldn't be surprised if takes many years for the retheme to occur in Orlando, but the change is inevitable.
I think the real reason there has been no update on the retheme is that Disney lied when they said [in June of 2020] that they had been planning the Splash Mountain retheme for at least a year. While Disney may have had some conversations about one-day retheming Splash Mountain to move away from Song of the South, I don't think the retheme was anything more than a vague, early concept. And then in the summer of 2020 — at the height of the Geroge Floyd protests — Disney quickly panicked and feared getting canceled, so announced way too soon that they plan to retheme Splash Mountian from Song of the South to Princess and the Frog to avoid being labeled racist.
Anyway, while I do love Splash Mountain as is, I think the retheme is a good call. It makes little sense to have an attraction advertising a movie that has been essentially self-banned by Disney. And Princess and the Frog needs more representation in the parks.
I think to make the retheme work, Disney is going to have to tweak large portions of Frontierland. Maybe the street leading up to Splash Mountain (with the Country Bear Jamboree and Pecos Bill restaurant) can be changed into a New Orleans-themed street? I've heard rumors about the Country Bear Jamboree possibly being permanently shut down sometime in the near future, so I wouldn't be surprised if this is the route Disney took.