How does an iPad interact with an Apple Watch or iPhone? It's going to be the same as that. They might do something funky like key in a VNC screen sharing session overlayed on top of the device to make it more readable, perhaps when the cameras recognise it, if you point the headset at the device, its screen could peel off into your window array etc.
But fantasies aside, it's probably going to be the same capabilities iPads currently share with other devices.