In the most bullish estimate for Google's Android platform yet, Gartner said the open-source operating system would grab 49 percent worldwide market share by 2012.
Gartner said Android would finish 2011 with 38.5 percent share and would significantly grow share the following year as Android handset makers slash prices to sell more smartphones.
Expect more Android phones in the sub-$100 range, particularly outside the United States where Android isn't already playing large.
"Android's position at the high end of the market will remain strong, but its greatest volume opportunity in the longer term will be in the mid- to low-cost smartphones, above all in emerging markets," Gartner analyst Roberta Cozza said in a statement.
Apple's iOS will grab the No. 2 position, with 19.4 percent share through 2011 and 19 percent share in 2012 on the strength of sales in the United States and Western Europe.
However, Gartner reasoned that iOS share would peak because, unlike Android phone makers, the company will seek to maintain margins rather than cutting new-product prices to gain market share. This will continue to limit adoption in emerging regions.
No. 3 player Research in Motion will see a decline in its share, from 16 percent in 2010 to 13.4 in 2011 and 12.6 percent in 2012, as the Blackberry maker finds itself squeezed by Android, iOS and Windows Phone in the consumer and business markets.
Gartner said it factored in RIM's migration from the BlackBerry OS to the QNX operating system for its PlayBook in 2012, bringing more advanced features than the current BlackBerry OS to boost its attractiveness in consumer and business markets.
Nokia, which is phasing out its Symbian platform in favor of Microsoft Windows Phone 7, will push Windows Phone to nearly 11 percent market share by 2012, and to nearly 20 percent by 2015. Windows Phone should edge RIM BlackBerry by 2013, and Apple's iOS by 2015, the researcher said.
For those who thought media tablets such as Apple's iPad or Android slates would eat away at smartphone share, think again. Gartner said these new devices would widen ecosystems, driving sales.
Gartner analyst Carolina Milanesi believes those who own iPhones, Android handsets or RIM Blackberries could end up buying iPads, Motorola Xooms or PlayBooks to pair with their devices to port their application experiences to a larger computing screen.
More broadly, Gartner said that the average selling price of smartphones would come down to $300 or less (without contract) and that worldwide smartphone sales would reach 468 million units in 2011.
Looking further ahead, smartphone sales will surpass the 1 billion mark by 2015, comprising 47 percent of the total mobile-device market, the research firm forecasts.