To show 3D, TVs output two separate screens alternating. Currently those screens vary only slightly, where the left eye sees one perspective and the right eye sees another perspective. They could make the two alternating screens display two completely different shows/games. One person could freely watch television. And on the same entire display-screen, another person could be playing a console game or be watching a movie.
Current technology says each of the persons must be wearing the two differently polarized glasses to allow the two view. The future will allow different polarizations to show up to people differently on the left and right side of the screen. The further future will allow televisions to distinguish between people and display accordingly for each.
Either that or everybody gets their own personal screens in front of their face.Now a quick word from a tech company who helps support me and this site: