iPhone S - 5.8" / 6.8" OLED, Face ID, Stainless Steel, Best Camera, 4x4 Antenna. Tri- Camera
iPhone R - LCD, Under Screen Touch ID? Or Face ID with a larger bezel at top or bottom to save cost. Aluminium, 2x2 Antenna. Double Camera
iPhone E - Basically the traditional iPhone design with Touch ID with slight update in Design. Single Camera
The three model will then just iterate on their own. May be the iPhone E could even be unapologetically Plastic!.
Although I think Apple will just continue its current model until things really break.