Benedict Evans has a very potent and concise presentation of why mobile OS adoption figures have extremely significant implications for the evolution of mobile platforms.
This issue makes it hard for Google to drive the agenda for new mobile technologies within Android: it will take at least a year after announcement before a meaningful part of the base has access to anything new. Hence the focus on Google Play services and on the cloud with things like Google Now - moving everything several layers up the stack from the intractable fragmentation problem, and making the hardware OS less relevant. But of course, this reduces further the reasons to upgrade your OS, and makes it much less likely that third party apps will do anything on Android that they don't do on iOS (system utilities and other minority interests aside).
Conversely, a developer can use anything that Apple announced in iOS7 and be confident it will work on all their users' devices. So anything innovative Apple does takes effect right now.