Maybe the reason why it was passed on for Orlando has to due with the Florida stormy climate. But that wouldn't hold water since Singapore has a similar climate.
If there is a new show at USF for 2026, it will likely take the form of a parade.
I think the lack of WaterWorld is just a mix of other projects being in the work and prioritized over WaterWorld for USF.
USF opened with the Wild Wild Wild West. When IOA was under development/under construction in the mid-1990s, the Eight Voyage of Sinbad would be designed as the park's stunt show, albeit a different theme. Simultaneously, Terminator 2 is being worked on for the park and opens up in 1996. So with those two projects in the works, there was no real need to push WaterWorld into USF.
Obviously, Sinbad wasn't well received and saw a pretty consistent flow of alterations to the storyline. Fear Factor (the show) then premieres in 2001, and the park wants to synergize with that IP versus WaterWorld... and opens up FFL in 2005 - great idea but the show isn't well received. Once they realize FFL is not great, the park/resort is in jeopardy with all resources diverted to Potter.
After Hogsmeade, UOR goes through a massive transformation with other major projects in the work that pushes WaterWorld off to the side.
History of Stunt Shows at UOR:
Wild Wild Wild West Stunt Show (USF) - 1991 to 2003
Terminator 2 3D (USF) - 1996 to 2017
Eight Voyage of Sindbad (IOA) - 1999 to 2018
Fear Factor Live (USF) - 2005 to 2020
Matt Hoffman's Aggro Circus (IOA) - 2010 to 2011
Bourne Stuntacular (USF) - 2020 to Present
Obviously, Universal deems WaterWorld a major success, so while it is shocking that Orlando never got it, looking at the timeline makes sense.