Gartner predicts:
Android will double from 505.5 million to 1.061 billion device sales from 2012 to 2014.
Apple iOS and Mac OS X will grow from 212.8 million to 354.8 million device sales from 2012 to 2014.
Windows will grow from 346.4 million to 378.1 million device sales from 2012 to 2014.