This year, Android will own the market, with 39.5%. Second is Symbian at 20.9%. Third is iOS at 15.7%. Fourth is BlackBerry with 14.9%. Fifth is Windows Phone 7 and Windows Mobile with 5.5%. "Others" bring up the rear, with about 3.5%. ("Others" most likely consists of HP's webOS, Linux, et al.)
"Android is poised to take over as the leading smartphone operating system in 2011 after racing into the number 2 position in 2010," Ramon Llamas, senior research analyst with IDC's Mobile Devices Technology and Trends team, said in a statement. "For the vendors who made Android the cornerstone of their smartphone strategies, 2010 was the coming-out party. This year will see a coronation party as these same vendors broaden and deepen their portfolios to reach more customers, particularly first-time smartphone users."
In four year's time, IDC expects a dramatic shift to take place, mainly due to Nokia's plans to ditch Symbian in favor or Microsoft's WP7 platform. By 2015, here's how it expects things to shake out: