All the big 3 (Windows, OSX, Ubuntu) do this now though. The old way is never coming back, or at least not anytime soon.
Indeed, you're correct. But this is a marketing problem with a marketing solution.
Imagine that, internally, Apple decides not to work on 10.11 for 2015 and instead plans to make Yosemite better in 2015 and pushes 10.11 to 2016.
Like you said, they can't actually do that anymore, they'll look bad compared against every other tech company.
So what to do? Well, they should just
do that, but just call it 10.11 anyway. It's all just marketing. Throw in some consumer-friendly features like new Mail and Calendar features and people are happy they have something "new."
So yeah, there'll be some changes, but those are in-app changes that won't affect other software. Things like Photoshop, printer drivers, and Fusion all keep working the same as before and OS X just gets better.
So you have a situation where alternate years get deeper changes underneath that developers notice (what we used to call "OS updates") and the other years get skin-level changes that consumers notice more (that consumers still call OS updates, but we know better).
Yearly updates but on on a 2-year rotating cycle.
I just totally made this up, but what if one of those cycles are called OS X and the alternate years are called OS X-
S years. I mean, where on earth did I come up with this crazy idea??