Perhaps it will be a mini projector, so if you put it up near a wall the whole tablet will be a keyboard (or whatever kind of input device) and the projected image will become the screen. This would be especially good for writing a lot, as otherwise you gotta lean forward too much and it will hurt your neck.

At least it will probably be there to allow for 2 screens, for whatever use you might have for that. I can't see it being a full blown projector capable of doing slides for a whole lecture theatre. The lens would be too big and too expensive.