I think that one of the least-understood facts about the competition between Apple's iOS ecosystem, Google's Android, and Microsoft's effort to re-launching Windows as a mobile platform is that worldwide smartphone penetration is still less than ten percent. Even in rich countries like the US, Canada, and Sweden less than half the population owns a smartphone. In Germany, it's below 25 percent.
I think that if you look at the situation realistically, the competition isn't between the major smartphone platforms it's between smartphones and non-use of smartphones. There's huge room for growth for any platform capable of delivering a decent product and the main issue isn't the Andoid-vs-iPhone sniping but supply bottlenecks of touchscreens and (especially) bandwidth. Apple couldn't build a billion iPhones (nor could Samsung build a billion Galaxy Nexuses) even if people wanted them, and even if they somehow built them all the mobile networks would crash if people tried to use them.