Well, I know that the original Model X concept (and, to be fair, the BMW i8 Concept) all had a mirrorless design and concept. Essentially, the rearview mirror acted as the screen to show you the full view around your car. It definitely takes getting used to because our eyes are trained to go that route. But, it is paving the way to the future. The issue with them comes cost. It's not the cameras that are expensive because cameras are relatively inexpensive. Rather, the problem is the costs associated with testing, R&D, driving with them, etc. Mirrors are inexpensive and work. Cameras have a lifespan, subject to malfunction, and require you to place display somewhere. The touchscreen makes sense to put it there, but you have to spend time perfecting the UX and UI for that.
Who knows though, part 2 may be just that and the mirrors go away. If they can pull it off and keep the car at $35K, would be awesome.