Not sure, but i hope they can be using vectors graphix. As then, when resolutions gets larger, the size of the icons wont, as we could easily resize them and they'll scale beuatifuly!!!
Olaf, in my interview with him, said, the icon system needs an overhaul. Icons are getting to large.
I think the icon system is unique for AmigaOS and needs to be kept, but i think myabe a different format for them, would be a good idea.