Google Inc.’s Android mobile operating system will be the big winner in the worldwide smartphone market share race come 2015, according to new projections by research firm Gartner Inc. BlackBerry will continue its significant decline, the iPhone will lose its luster and today’s also-ran Windows will bounce back to life, the firm predicts.

Worldwide, consumers using smartphones running Android will account for 38.5% of the market this year; iPhone 19.4%, BlackBerry 13.4% and Microsoft Windows 5.6%. In 2015, Gartner says consumers using Android phones will account for 48.8% of the market; Windows 19.5%, iPhone 17.2% and BlackBerry 11.1%. The remaining market includes smartphones running the Symbian operating system, which is in great decline; Palm WebOS, which has been consistently dropping; and other smartphones, Gartner says.

“As vendors delivering Android-based devices continue to fight for market share, price will decrease to further benefit consumers,” says Roberta Cozza, principal analyst at Gartner. “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.”

It’s in emerging markets where low-cost Android phones can boost Android market share across the globe. But Gartner does not break out smartphone market share for the U.S., where there are more consumers willing to shell out more money for high-end devices like the iPhone. Gartner predicts the iPhone will remain the second-biggest platform worldwide through 2014 despite its share deceasing slightly after 2011. This reflects Gartner’s underlying assumption that Apple will prioritize maintaining margins over pursuing market share by changing its pricing strategy. This, Gartner says, will continue to limit iPhone adoption in emerging regions.

In the U.S., The Nielsen Co. says for the three-month period ending in January, consumers using Android phones accounted for 29% of the smartphone market; iPhone 27%, BlackBerry 27%, Windows 10% and Palm 4%. This represents continued growth for Android, stable ownership for the iPhone, and continued declines for BlackBerry, Windows and Palm.

On the tablet front, Gartner says that, despite mounting competition from tablets running other operating systems, Apple’s iPad will continue to own the majority of the worldwide tablet market through 2015. 69% of tablets in use will be iPads this year; that number will drop to 47% in 2015. Consumers worldwide using Android-based tablets will account for 20% of the market this year; that number will jump to 39% in 2015.

Again, Gartner does not break out U.S. sales. Other research firms do, however, and they say the iPad is much more dominant in the U.S. than Gartner’s global estimate would suggest. EMarketer Inc., for example, says the iPad owned 88% of total tablet sales in the U.S. in 2010; that number will drop to 81% this year and 74% in 2012, eMarketer says.