For Future World, I truly think it'd be best not to add a new pavillion in either of the two (or maybe only one) remaining expansion spaces. And on that note, I do not think Wonders of Life should reopen as a standalone pavillion. Unpopular opinion, but I will try to explain.
Wonders of Life's fundamental problem, and a significant cause of its closing, was that it was tucked away. Unlike all of the other pavillions, you couldn't really see it until you got close. There was no good weenie to draw you in. Only a sign and the spiraling thingy, but that paled in comparison to the other six big, visible buildings and Spaceship Earth. Now that may not seem like an issue to us experienced people, but the average new guest is very much "see and do." So if they don't see it, they miss it.
Now, I suppose if Disney were to try again, they could squeeze the added pavillion closer to the walkway and build some bigger weenie to draw people in. But, one, that would hurt the symmetry of Future World. And two, that would severely overcrowd a section of it. And so by adding, they'd actually be subtracting. How so? Because the open space around the visible part of each pavillion is what defines it. It's what makes it appear more grand. It's what triggers the average guest's brain to know that this is important, this is something good. That this is something they should see and do.
The expansion pads are so tight that almost all open space would be lost. And so the new pavilion, along with the older ones butting up against it, would all appear less grand.
So there really is no good way to add another Future World pavillion. Is there?
I'd be far far more in favor of them doing what they did with The Land pavillion, adding another ride/attraction out of guest view that uses the expansion space. That way, the park aesthetics remain intact. And each pavillion becomes an even more solid experience. I believe that is the best long-term vision for Future World.
I hope I explained that clearly. It's a tough concept for me to put into words.