You would think with all the smart, detail oriented, outgoing people at apple, SOMEONE would have pulled the person responsible for shifting to a yearly cycle and tell them: "look, this accelerated release cycle, it's not resulting in quality software. It's hurting our reputation. It's not performing on 2 year old hardware. People are losing faith in our ability to release stable bug-free builds. Users shouldn't have…
I don't even understand who they're competing with by doing yearly updates. It's probably a big scramble to get features released and for what? To beat Windows 8? To beat linux? They don't have any threats when it comes to desktop operating systems, so they should slow down and make some quality updates.
In terms of market share, OS X is to Windows as Windows Phone is to iOS. Sometime about a year ago, Windows 8 alone already had higher market share than all versions of OS X combined, and has only been increasing the lead since.
Windows 10 is looking to be the spiritual successor to Windows 7, combining the improvements that came in 8 with a UI that's more palatable for many. And, now there are ample PC hardware options that rival or surpass Apple's in many aspects, which is a lot of what sold MacBooks to average consumers in the past.
I would guess that Apple is taking Windows 10 very seriously.