Looking at the big red 1 on both my parents' iPhones' Settings app (not mention the much higher numbers on the App Store app) when I visited them this weekend, I imagine the same segmentation exist on iOS. Different proportions and easier upgradability on iOS, but the basic idea is the same on both platforms. If you want updates, you are able to get them. If not, and most don't, it is no loss to anyone but developers and security.
You can imagine the same segmentation, but you'd be wrong about the end result. 4/5 of iPhone users have updated to 5, while less than 1/10 of Android have updated to 4.
As a service provider, we see the device stats in our logs across tens of millions of users, and the numbers line up with Apple's slide: over 80% of iOS devices are updated to iOS 5, and under 7% of Android devices are on Android 4.
And really, it's a lot worse than that, with variations in the 2.x releases, even within the 2.3.x releases, affecting whether devices are able to stream video properly or not.
