Superphil
Dismember
A lot of modern stadia have translucent roofs - it allows sunlight through and hence faciliates better growth in the grass. I can't see what photo you mean, but we probably would end up with a glass-effect roof, so you may well be correct.
I had the pelasure of attending one of the 1901 club presentations last night. We were told the roof is going to be blue, with white fittings, so I'm not sure if what you are seeing are the final roof parts.
Interstingly, I hadn't realised it but the reason why there are stanchions holding up the arch, and will be holding up the other one, is that until the roof goes on and is attached, the arches would fall over backwards. The roof panels and supports actually tie the two arches together.