Pop quiz: How long does it take for a new version of Android to be widely adopted? A new version of Android comes out, AOSP updates, OEMs adapt it to a myriad of devices, and carriers test the updates. That process. How long does it take?
It's a tough question to answer, mostly because Google doesn't provide data like that. The official site shows a 6 month version history, and that's it. Anyone looking for a decent amount of data is out of luck. There’s no way to view the long journey older Android versions have taken, and no way to see the bigger picture of how the update process eventually works out.