The broken lines show portions of the electronic device which form no part of the claimed design.
The only things that aren't broken lines? The basic shape of the housing.
But you raise an interesting point: If high-profile apps such as Minecraft are available for x86 but not ARM, what are the chances of the ARM platform ever taking off?
I've always assumed that was kind of the point. Windows RT strikes me as the "embrace" phase of the Wintel Master Plan To Deal With ARM®.
I think if we're honest, Valve's big complaint about Windows 8 has nothing to do with "performance" or expected sales, it's more about "waah we were about to launch an application store but now thanks to Microsoft's we won't have a virtual monopoly on that for Windows."