You'll notice all the demos of macOS Big Sur were shown using a Pro XDR Display, connected to hardware that was later revealed to be the MacMini+A12Z/Developer

You'll notice all the demos of macOS Big Sur were shown using a Pro XDR Display, connected to hardware that was later revealed to be the MacMini+A12Z/Developer Transition Hardware. And during the Maya demo, it was a Pro XDR Display explicitly connected to the Developer hardware. Which is interesting, because the Pro XDR Display can only be driven TB3 [1]. So Apple figured out the licensing for a TB3 controller chip to work in this design (which funny enough would be licensing that IP from Intel), or they are using USB4/TB4, or something else I'm not smart enough to think of. 1- https://www.apple.com/pro-display-xdr/specs/ https://www.apple.com/pro-display-xdr/specs/