It could be the most impressive from a technological standpoint and on ride aesthetics, but imo, nothing in Future World still is a better ride experience than Spaceship Earth, and I HIGHLY doubt that will change when TT opens.
The problem with Future World in it's current state (beyond the obvious lack of additions and letting Pavilions become convention space) is that it's a mixed bag of different ride systems, many of which are impressive (TT, M:S, Soarin, etc.), but the problem has a lot to do with lack of attractions throughout future world and lack of vision. All of those rides I mentioned have, at the time of opening, new ride systems, but it's all wasted as these things are not updated as they should be (Soarin') or the ride had a so-so reception (M:S).
TT was a first gen of it's ride system and the ride system has since advanced. Despite this refurb, placing RSR over at DHS will make TT look silly. Same goes with a Soarin-esque Pandora ride. Things like that automatically make the other look bad in comparison. Epcot needs to do something quick. Either something completely new, or a refurb to Imagination or Energy would help. Imagination needs a full pavilion makeover, meaning EO needs to go. And any new version of the ride should involve a trackless system, or it's almost not even worth it. It's the perfect ride to do it with.
- - - Updated - - -
To add on to that, it should be interesting to see what happens with M:S seeing as the 10 year contract expires next year I believe. I'm rooting for Disney to ditch Hewlett-Packard and get SpaceX to sponsor the damn thing and hopefully get a true space pavilion.