Tomorrowland has definitely been the subject of many threads on these forums lately. I've been following a few threads closely and have come up with some ideas for possible updates. I'm not going to focus on replacing any current rides in the land. This will mostly focus on providing ideas for the overall theme for the land and an exciting new E-ticket ride.
Tomorrowland would receive new facades. Imagineers wouldn't have to go too far to get inspiration. The new tomorrow land is inspired by another famous Disney building that already exists today. Yes I am indeed talking about the Walt Disney Concert Hall in Downtown LA. The overall aesthetic would also feature lots of glass.This style would allow current achitecture found on Space Mountain and Star Tours to blend into the new theme for the land with little modification. Many of Tomorrowlands rooftops would be fitted with new rooftop solar panels in the process.
Now to the centerpiece for the new vision of Tormorrowland. The entire Autotopia would be removed. The entire area would be excavated below ground to make way for a large cavernous show building that would allow for a new "Sister" mountain to to Space mountain to be added. If Space Mountain is your journey through the darkness of space this new sister mountain is your journey through the city of the future. The interior of the show building would feature a flying rollercoaster (track is above you) that would simulate a flight through the city of the future.
You start of by walking through an entry tunnel much like you do currently with Space mountain. You walk over a glass bridge to the queue. You board the coaster and leave the loading station. you prepare for launch much like you currently do for California Screaming but you find yourself in dark spiraling tunnel much like you do in Space mountain. As you drop the tunnel transitions with projections simulating your re-entry into the atmosphere and find yourself above a futuristic skyscape.
The roller coaster would weave in and out of the tops of the highest buildings of the skyscape utilizing a forced perspective optical illusion that you're flying high above. Think Peter Pans Flight of the future on steriods. The monorail beam would weave through the the coaster structure at various points of the show building and would appear to be traveling along side you at points on a floating beam. The pilars would be painted to blend in with the cityscape or sky below. As you make your final approach back to the loading station you go under the monorail beam and under the glass bridge that you walked through when entering the queue
The building would include a relocated monorail station. The station would be accessed using an incline moving sidewalk/escalator at the end of the entry tunnel. the monorail station would be exposed to the interior of she showbuilding with a view of the skyline and the roller coaster flying by. (Think Blue Bayou looking into Pirates)
The Mountain large show building would mostly be underground with the monorail beams passing through the show building through multiple points. The Appearance of the mountain itself would blend into it's surroundings on the Fantasyland side as the fantasyland side would be mostly rock work that slopes up towards Harbor Blvd. The inspiration for this came from the design of Spaceport America that is currently being built in New Mexico. The design of the of the slope intends for the large terminal to blend into the surroundings. To see what this actually looks like this short youtube video shows how this could work.
Spaceport America Eco-friendly - YouTube
Sorry I forgot to remove the majority of the Autotopia queue in the image above but most of that would end up as open space to aid with traffic flow.