Disney has really gone out of its way to avoid mentioning Song of the South as much as possible. While media outlets have made the connection that Disney is replacing Splash to get away from the SotS theme, in all press releases released by Disney related to the retheming there hasn't been anything said about SotS...just statements about the power of diversity and how Tiana is inclusive. I honestly don't think Disney will ever fully address the Song of the South controversy.
For example, in the Imagineering Story on Disney Plus, Angela Bassett makes one brief comment about how Splash Mountain is based on "an old, problematic movie called Song of the South" and she gives no further elaboration. The documentary did not explain:
1. Why Song of the South was problematic
2. Why Song of the South was chosen as a theme in the first place
3. How the Disney company's relationship with SotS has evolved since the development of Splash Mountain. SotS was released FOUR times between 1972 and 1986. In that era of Disney history, it was a profitable movie and generally regarded as a Disney classic by white Americans (it did still receive criticism from Black Americans, but the criticism wasn't as prevalent as the original 1946 release).
The documentary could have said how the ride wanted to capitalize on the Brer characters (which were popular in the parks at the time) while leaving behind the more offensive and racist aspects of the movie (The plantation setting, Uncle Remus, the Tar Baby, etc.). But Disney didn't do that because they didn't want people to dwell on Song of the South or the past mistakes they made.
I believe that once the retheme does happen, it would be a good opportunity for Disney to have a "Behind the Attraction" episode that explores the creation of the original Splash Mountain and thoroughly explains WHY it was problematic and why it was rethemed to Princess and the Frog. But knowing Disney, I doubt such a serious and uncomfortable topic like that will be addressed.