My take on this is that a lot of smartphone users don't really care that much about apps beyond the core features that come with their phones. These people are happy with Android phones because the Android email & web apps are as good as, if not better than, their iOS equivalents. If you look at Apple's app store sales its really games that are driving their volume and I think a lot of people just aren't that interested in mobile games.

So I won't be surprised if Android continues to develop market share but never becomes quite the same app ecosystem.