How about the Observatron? When it works it seems to be monitoring space for messages from ET:)
I think Tomorrowland is VERY futuristic - if we are taking a post apocalyptic future, ie Mad Max!!! With everything rotted and rusting, and in a vast wasteland.
Sadly Tomorrowland is kind of a waste of space right now. But then so is Rivers of America is you really think about it.
But pirates aside, I still immensely enjoy the atmosphere that the Rivers of America add to New Orleans Square, as well as Frontierland and Critter Country. It's hard to imagine those lands without the beautiful view of the water sparkling in the sun with the Mark Twain slowly making its way around the riverbend. Plus the Mark Twain Riverboat, Sailing Ship Columbia, and the Davy Crockett's Explorer Canoes are all wonderful, immersive experiences and a great diversion from the park's more elaborate E-attractions. Their beauty is their simplicity. They effectively serve the purpose that they're intended to serve. So I really wouldn't consider the entire area a "waste of space". Maybe the island at the moment, but not the river itself.
The problem with "tomorrow" is its a moving target. Attractions are outdated as soon as they are built. I think WDI was smart with EuroDisneyland and the substitution of "Discoveryland" for "Tomorrowland". "Discovery" is a much broader concept than "Tomorrow" and all the current attractions (at all the Magic Kingdom Parks) fit into the category of "Discovery" and as so many above have pointed out above, its a stretch to characterize current attractions as "Tomorrow".
And if these ideas do become outdated by the time they're built... who will even care? We'll be too busy traveling through time and having fun shrinking ourselves down to tiny sizes.
O.K. so maybe an Avengers based attraction doesn't fit into the category of Discovery or Tomorrow.
It's not like Mickey Mouse where nearly everyone has a connection and he is sort of a symbol for the "everyman." The Avengers? Quite a bit detached from anyones life experiences. Except the fanboys of course...
However if if there is a central story element of clean energy or some technology that will benefit mankind and the Avengers are used as a tool to move that story along, there is a good chance that it will fit those themes.