Oddly enough, Electric Umbrella (and before it, Stargate), Odyssey, Cosmic Rays, Tomorrowland Terrace have the fitting aesthetic I think. The former two obviously already fitting with the EPCOT design language. I don't know what exact style this is, I'm calling it retro futuristic, and IMO it doesn't date. It's simply a style. What dates it is when you put contemporary design into it. Electric Umbrella decor screams 90s doesn't it, but circular bays, raised platforms, shapes etc, give it the timeless style. The Communicore buildings were built that way, Odyssey too, and of course every ex-Future World pavilion has its own avant-garde take.
In close proximity to Connections you have Spaceship Earth (and Project Tomorrow), the wedge-shape ex-Energy building which is now Cosmic Rewind, Mission Space which is a later addition but still has that retro-futuristic, whimsical style. Of course, the Connections buildings externally retain the same style, but internally they've gone for a style that matches what they were intending to do with the new central gardens and what is probably the same contemporary look that they are remodelling other areas of WDW with (World of Disney, Creations, hotel rooms).