A rear camera is mandatory on new cars in the US these days, and it's honestly a good idea to have them either way. This makes a screen a necessity more or less no matter what (I can't see it being implemented with a bring-your-own tablet solution).
That doesn't mean they have to ship most of the infotainment system though. They could just leave that hole there for Carplay to fill. But that would be admiring defeat, and we can't have that.