The three basic quotes to keep in mind are these (and forgive me if I mis-quote here; doing it all from memory):
"Disneyland will never be completed. It will continue to grow as long as there is imagination left in the world."
"Disneyland is NOT a Museum."
"If you're going to replace an older attraction with a newer one make sure it's more elaborate, more sophisticated, more amazing than the one previous."
Keeping those three quotes in mind, what Disneyland attraction would you take out, and what would you replace it with. No fair retro-replacing such as putting the old Country Bears back in place of the Winnie The Pooh fiasco... if you're gonna bring the Country Bears back you have to explain how it's gonna be bigger and better than ever before.
Now let the ideas flow!
REMOVE the Victorian/Jules Verne-esque copper-and-Brass theme from Tomorrow Land.
REPLACE it with a generically Star Trek/Star Wars theme incorporating bright "Neon" blues and reds on a beige contoured background. Touch-panel help screens with recorded voice information should be plentiful along the walkways... think of the same technology that they used at Disney World for the interactive Mickeys, only in a stationary place. Guests could use the touch screen to see what the wait time for a ride in Fantasyland is like, check the menu and prices of different eateries in the park, check show times... al with a pleasing futuristic computer voice telling them the information. Make Tomorrowland look like TOMORROW once again :)