Actually, if they could figure out how to move some backstage support buildings behind Seas, there's as much room between Seas and Land to build a pavilion as there was for WoL... There's a VERY large grassy area between Land and the bus parking lot. It's just ripe for a good-sized show building. (Which is why I was surprised that they built Soarin' on the Food Rocks side of Land and not Circle of Life side. They possibly could have avoided the World SHowcase sightlines problem altogether...) In fact, going by the aerial image on Google Maps, there's even already a small spur off the walkway where a path could lead up to this pavilion's location. Though I don't know where exactly the Nemo sculpture was placed around here.
I, too, recall hearing about expansion into a "second loop" of countries. Not sure how/if it would work, though. There's a canal back there just on the other side of the access road.
-Rob