Some of the Older Model X concept imagery had rear view images on either side of the speedometer in the instrument cluster, presumably from the two rear cameras. Honda replaces the center console display with the "LaneWatch" camera feed when you trigger the right turn signal - they also have a lever to display it at other times.
Tesla could easily take either of these approaches, or do something more sophisticated, like replacing the rear view image that you can display on the center console with a fused combination of the three feeds. They've also been working with a company that makes video capable rear view mirrors (as in, the center mirror on the windshield can display a camera feed with data superimposed or be a mirror.)
I don't think anyone who isn't under an NDA knows what they'll do, but it'll be interesting to see.
Walter