This idea that Apple pushes off updates to future releases just as a reason to drive upgrades is a fallacy. Given Apple's scale required for production, raw material sourcing, tool development and production, global shipping, marketing, etc., they have to make decisions on products close to a year in advance - and some of the things they hope can make the timeline one year, end up getting pushed out to future releases because either the technology isn't fully developed, or the supplier of components can't deliver enough product that meets their qc requirements, timeliness, etc.part of it is the need to spread the updates over the years. they know that mearly updating the look of the watch (flatter sides, smaller bezel, etc.) will be the feature that triggers updates this year. why "waste" putting new biometric sensors in this year when they can use it to drive upgrades for the Apple Watch Series 8 and 9 which likely will look exactly like the 7? wish it wasn't this way but that's the deal...
I'm sure Apple has a roadmap of what they want the Watch to offer going out perhaps 5 years, but they also have contingencies for features that may not make the cut, and the timing they need to shift to plans B or C prior to their putting in orders for components.
This idea that their roadmap includes "hold back feature for future release" is crazy thinking, at best.