I think from a marketing perspective Apple has this covered, sort of. Even if they go backwards from 5X to 3.5X, the crop zoom from the 48 MP sensor also provides the 7X option. 3.5X is advantageous over 5X for portraits, whereas 7X is a further reach than 5X. I realize that cropped 7X isn’t the same thing as true 7X but I suspect it’s a compromise Apple thinks will go over well with most consumers, including myself, which is why I think this rumor may actually be true. With just three sensors, the 16 Pro offers 4 “optical” zoom options, but the 17 Pro would offer 5:
The current 16 Pro is 0.5 / 1 / 2 / 5X.
The 17 Pro would be 0.5 / 1 / 2 / 3.5 / 7X.