Two estimates by two different market research companies have projected contrasting results for Google’s Android.

While eMarketer said that Android is on its way to displace Apple’s iOS by the end of this year in the smartphone market in the US, the International Data Corporation (IDC) said that Android-based media tablets are expected to cede worlwide market share in 3Q11.

eMarketer has predicted that by the end of this year, the iPhone will have lost its title as the No. 1 smartphone in the US, with Google’s Android operating system surging ahead to first place.

The market research firm said that Android will be installed on 37% of all smartphone handsets in the country by year-end, up 13 percentage points over 2010.

It said, "Apple will likewise see its OS increase share, but only slightly: from 28% of the market last year to 29% this year. iOS will continue to inch upward in market share through 2013, but by that year Android will hold more than two-fifths of the US smartphone market."

The growth in Android usage comes mostly at the expense of Research In Motion’s BlackBerry, which eMarketer predicts will drop from 30% of the market in 2010 to just 15% in 2013. Shares for Microsoft’s and other competitors’ operating systems, including Nokia’s Symbian, will also dwindle over the forecast period, said the company.

"The battle for US smartphone market share continues to look like a two-horse race between Android and iOS," said eMarketer Principal Analyst Noah Elkin.

"Within two years, Google and Apple will control nearly three-quarters of this key segment, making it very difficult for contenders like Microsoft and RIM to achieve scale," said Elkin.

Meanwhile, IDC said that strong demand for Apple’s iPad 2 fueled worldwide media tablet shipments in the second quarter. iPad 2 saw shipments reach 9.3 million units, representing a 68.3% share of the worldwide market (up from 65.7% the previous quarter).

BlackBerry maker Research in Motion (RIM) also benefited by entering the media tablet market in 2Q11 with its PlayBook product, grabbing a 4.9% share of the market, said IDC.

The company said that Apple’s strength and RIM’s entrance meant bad news for Android-based media tablets, which saw its collective share slip to 26.8%, down from 34.0% the previous quarter.

IDC expects Android to cede additional market share in 3Q11 (dropping to 23%) before it starts growing its share again in 4Q11 (increasing to 25.9%) and beyond.

Mobile Connected Devices research director Tom Mainelli said media tablet shipments grew at a solid pace in the second quarter, led by continued strong demand for Apple products.

"We expect shipment totals to continue to grow in the third and fourth quarter, as additional vendors introduce more price-competitive Android products into the market and Apple works to maintain its dominance in the category," Mainelli added.