While I know this was the original rumor, I find it hard to believe that Disney wouldn't have eventually rethemed Splash at WDW. Maybe (very small maybe) they would've chosen a different IP.
I think what happened was, an imagineer came up with the concept of retheming DL Splash with Tiana since her story takes place in New Orleans and their Splash is adjacent to New Orleans Square. Disney heard the idea and was like "wow this is a great idea, how do we make it fit in both parks?" And then we wound up with the story and attraction that is coming real sosoon.