While we don't know the exact material or color, it's quite clear from the foundation and steel structure thus far that this will be nothing more than a box. Based on the framing we can tell that the siding will be a lightweight material (if I were a betting man, I'd put money on insulated metal panels) without any meaningful shape/depth/protrusions to add architectural interest or theme.
They can pick whatever color they want. They can paint a giant mural on the side. They can attempt to landscape the perimeter to make it disappear (at that height, good luck!). But none of that changes that it is a very utilitarian structure on a very large scale. It's a box that will look like a box, and will tower over almost everything in the park.
The most dimensional treatment we can expect is some inoffensive contrasting trim and accent panels, like what DL is getting on the back (parking garage-facing) side of their Star Wars project. It may be the best-looking warehouse in the industrial part of Anaheim, but it's a long way from being "good architecture", let alone the iconic futurism we've come to expect in Future World.
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With the GOTG build roughly twice as tall, it may be better to go for something bland, to keep the eye from focusing on it. And when your best plan is to hope that people don't notice the elephant in the room, you haven't done a good job as a designer. If only the existing empty buildings in Future World were big enough to hold compelling attractions of their own...