I have decided that
this from their front page, must indeed be a photograph of the prototype figure:
now it looks like a tongue, and judging by the texture I'm guessing its plastic. Which means the entire head sculpt will be plastic and not rubber as i first thought. Also the fact that we see its tongue suggest that its mouth is jointed. And If they plan to add PERS (which i'm hoping cause, theres plenty of room in there ) An opening jaw would provide easy access to the controls. Also note that the tongue is extending beyond its teeth, which makes me wonder if the tongue itself is jointed, hmmm...
There is also the question about its body. The Martians neck is very thin, so connecting it to any True Type would make the body look out of proportion. Unless they plan on hiding the body with the costume, which would still be out of scale anyway. So a custom body seem very likely but what kind of material would it be made out of? I think they might do something similar to how the 'Alien Dog' is constructed with a rubber skin suit around the body maybe.