Again (And I know that this news is going surprise a lot of you Pixar fans) no. Many of the attraction's pre-existing settings & set-pieces are going to stay right where they are. And -- yes -- that included that silly-looking sea serpent.
"But -- if that's really the case," you sputter, "Then how is any of this 1950s era stuff ever going to fit into an attraction that's supposedly based on a movie that's as colorful & stylish as 'Finding Nemo.'?"
To quote "The Hitchhiker's Guide to the Galaxy," don't panic. The Imagineers have come up with a clever plan to fold new elements from "Nemo" into existing parts of the old Tomorrowland attraction. With the end result being a new-ish Disneyland ride that tells one rather funny story.
Take -- for example -- how the Sub's old "Lost City of Atlantis" sequence is going to fit into "Nemo" 's new storyline. Think back to the scenes from that film that were set in the dentist's office. In particular, how Gil, Bloat & the rest of fish who lived in the aquarium used that fake underwater volcano as part of Nemo's initiation ceremony.
Well, after they finally escaped from 42 Wallaby Way, what better place could there be for the Tank Gang (Who clearly enjoyed getting dressed up & doing ceremonial chants at Mount Wannahockalougie) to set up shop than at the base of a real underwater volcano?