An alternative is to use the following formula derived from the linear interpolation of the two measured market shares. iPhone market share is y/(1+y) where y=0.21x and x = F/(1-F) and F is the expected market penetration of smartphones.
So if F = 91%, x = 10, y = 2.11 and therefore the iPhone market share = 68%.
We also know from the plot of the market that F = .91 is reached around February 2017. So we can suggest that at 90% penetration (approximately saturation) the iPhone will have 68% market share of users in the US. Forecasting the addressable market (US population aged older than 13) at about 266 million that implies 180 million US users of the iPhone by early 2017.
Unfortunately Dediu does not share the data that he used to arrive at that conclusion, so take it with a grain of salt for now and do note that things can and will change, as a variety of factors out there can affect the market and consumers’ buying behavior. In any case what do you guys make of Dediu’s predictions? Will Apple eventually come to dominate the mobile space?