I've always wondered what the area around Splash was actually themed tooAgain - Splash Mountain was inspired and set around the South and Georgia.
Princess and the Frog is set in Louisiana - the beginning of the "Frontier". They aren't going to make the mountain turn into New Orleans, and a bayou is certainly fitting in a Western setting - It's just a matter of execution. The concept art doesn't show anything that makes it "not fit" at this time.
Right now it's just a pretty mountain to me