E.T. should stay because it's part of USF's history - a relic of an era focusing entirely on the practical. Considering there are other spaces to use for expansion or renovation of the park (Shrek, T2, the MIB/Springfield plot, Fear Factor and the surrounding land, some of the soundstages by Rockit/DM, the old parade building in KidZone), it's better to let a classic stick around and preserve some of Universal's history.
I'd think this could work as Universal Studios Florida's 15 to 20-year plan:
E.T. complete overhaul (immersive outdoor queue starting by Gardens of Allah, new pre-show, spaceship RVs offered once again for those under the 34" height requirement, brand-new AAs, projection effects)
Super Nintendo World (Mario Kart E-ticket, Donkey Kong E-ticket, Yoshi D-ticket)
Woody Woodpecker repurposed as a Krustyland/Itchy & Scratchy coaster
Super Silly Fun Land in the rest of the MIB/Springfield plot (Minion Mayhem E-ticket family boat ride, SSFL play area, Dr. Nefario flat ride like Junkyard Jamboree)
Fear Factor and MIB used for a general London expansion (Sherlock walkthrough, Doctor Who E-ticket, James Bond stunt show, mini-London Eye along the waterfront)
Mummy total revamp featuring cohesive storyline, new characters, brand-new AAs, more projections/theming in the coaster section
Simpsons Ride upgrade, including Treehouse of Horror overlay for Sept/Oct
DM - Minion Mayhem, Shrek and the current Universal store replaced with a new entrance plaza, a walkthrough museum (replacing part of the old Minion Mayhem), and Greatest Cinematic Moments E-ticket (three-stories, all-ages, features old-school Universal IPs for the most part but there can be newer ones like Bourne, replacing Shrek)