I think that 12 Pro Max main camera sensor is here to stay for another generation or two or three. Anything bigger would require major re-design...the camera bump of 12 PM is already ginormous.
Of course, software will be better due to A15...maybe Deep Fusion and Night Mode processing will be instantaneous.
I think that Apple will focus on improving Telephoto lens and ultra-wide lens. Right now, there is a HUGE gap in image quality b/w main sensor and these two “accessory” lenses. Personally, i only use Telephoto for Portraits (in good lighting). That’s about it. I use UW lens for landscape in excellent lighting. (The addition of Deep Fusion to UW lens is much appreciated by me.)
If Apple can make 2.5x telephoto lens have a bigger sensor AND go back to f/2.0 (f/1.8?), then that would be gravy! No reason not to...given that 12 PM telephoto & UW lenses have increased in size (for no benefit other than aesthetics) just to match the main sensor. The UW lens sensor can be bigger too. I hear about f/1.8 lens for UW next year...i have my doubts that it would be this wide aperture...my guess is either f/2.2 or f/2.0 at most. My guess is slightly bigger UW sensor and f/2.2.
I doubt that we will see periscope...because that would require again major surgery to the current design.