Much of the history of GUIs can be split into two parts:
The quick shift from skeuomorphism to flat design happened in the midst of other cultural changes: the prevalence of “digital natives,” specialized subnotebooks (e.g. personal organizers) being replaced by more general computers (e.g. smartphones), society becoming more digital, along with the increasing abstraction of technology over the decades. These factors generally benefit flat design, which is why I don’t see it being replaced in the near future.
Ten years ago, iOS 7 and Mac OS X 10.9 “Mavericks” were probably near the top of my head.
Now I have to look up what the current versions of iOS and macOS are.
If Apple moved to a 2-year cycle, would you prefer Apple update all their OSes in the same year or update different OSes on alternating years?
I feel like a 3 year cycle for macOS, iOS, and iPadOS is probably ideal at this time. Apple already uses the dot updates for nontrivial features anyway. visionOS and watchOS are newer so should get more frequent updates for now.
W for Apple