When will the US reach smartphone saturation?

Horace Dediu graphs the ComScore market penetration data on smartphone platforms. We’re currently in the middle-late stages of the curve, which means that we’ll start seeing ever more increasingly tough battles over users as new users become fewer and fewer and churn amongst platforms becomes a real player. The first obvious note, is that whatever Microsoft is planning to do with Nokia it had better get to market and in a big way soon. The other point of consideration has been android’s slowing rate of growth in the US market. Will that continue and does what happens in the US have any predictive power elsewhere?