iPhone 6 debuted larger screens and Apple Pay, 6S a year later fixed the issues with the generational jump started by the 6. iPhone X debuted the notched edge to edge screens with FaceID, XS/R/Max like the 6S fixes the generational jump started by the X with its improved FaceID, etc. We all know what followed the 6S - the 7 was a very minor upgrade, main things being the water resistance and haptic home button. I'm not sure if we'll see an all new generational leap with the iPhone 11. So what else is left at this point for Apple to do? Apple has a tradition of hitting the sweet spot a year after a generational jump product release - iPad 2, iPad Air 2, 2013 rMBPs, etc. If the teething problems are worked out that some are experiencing with the XS, I totally see this as the next 6S type iPhone.