The latest data from Google shows that the Android activation rate is increasing at a relatively steady rate (i.e. acceleration is constant). The data provided so far is in the blue circles below. The green line is the interpolation and extrapolation of that data.
As the graph is projected forward we get an activation rate of one million per day by mid August of this year. If it continues then we could see 1.5 million per day by end of 2013.