I'd love a Space pavilion. In fact, how about Mission Space opens up into a Space pavillion once the ride is over. However, for people who don't want to ride a thrill ride, a Seacab-esque omnimover can take you into the pavilion as well. And space is awesome and 100% timeless, making it the perfect new pavilion that can draw in anyone.
Honestly, I think it would be cool if every pavilion had both education classic Epcot Center-type exhibits/attractions AND more modern TT/MS/Soarin'/Nemo type attractions. Imagine if Test Track and World of Motion wrapped around each other in a huge full Motion Pavilion that ended in a showroom, or if elements of Seabase 2021 and Nemo were mixed together.