iPhone Flip
https://www.youtube.com/watch?v=0ZU95ItQV58
A super professional concept video, but this style of flip makes no sense to me. You may get a more pocket friendly device, but the compromises required would be far too numerous to make it worthwhile. And, how many people actually struggle with the size of their phones these days?
It is possible that a horizontal flip iPhone may work, but it would have to offer real world benefits that make it worth the compromises. A bigger screen is fine, but likely Apple would want to make a device that can actually be used as a very small laptop style tool as well. That may work...