One thing I've noticed in all the clips for the movie is that the cape, while entirely CG, has a very specific, almost plush, texture to it- similar to crushed velvet. Also the way it billows implies it's relatively light. All this contrasts with the harder, rigid suits with their more mechanical, repeating texture.
Not saying it would be impossible to do it sculpted, but I can see some kind of material fabric mimicking the contrast between the two surfaces a lot more intensely than trying to get the same contrast all in polystone. But I do realize there are talented guys out there who could probably rise to the challange- if the art director bothers to make this a point. An yeah, I'm surprised that they are going with fabric on the main body of the suit. Looks spot on and in scale though.
I'm not usually a fan of fabric/mixed media on 1/4 scale or smaller- but in this case I think it will be the right way to go.