Correct me if I'm wrong, but couldn't Microsoft just release (or ship this product with) a sort of blinder to put around these glasses to make the dedicated sight come from the glasses themselves while darkening everything else?
Certainly possible. It'll be interesting to see how feasible it is for these goggles to render entire 3d worlds in this scenario, since normally they'd be rendering a small fraction of the space you're in.
If the speculation about creating opaque holograms is correct, you can just use a virtual blinder as well - a black hologram that obscures or creates a virtual stage.
