IDC Sees Windows Phone Passing Apple’s iOS in Smartphone Share by 2015

It’s popular math to do a long range forecast and predict that Apple by itself will gradually be passed up by operating systems used by multiple hardware makers.

And, all things being equal, that has been the case. Think back to the Apple II/Mac vs. DOS and Windows, for the most prominent example.

The thing is, all things haven’t been equal for at least the past decade. The iPod has thoroughly dominated the music player market, for example. And so far Apple has managed to maintain a significant share of the smartphone market and dominate the still-quite-nascent tablet market.

However, IDC predicts that Apple will be passed up in the coming years, not just by Android–a common prediction–but also by Microsoft’s Windows Phone 7.

In a new report, IDC projects that by 2015, Windows Phone 7 will power 20.9 percent of smartphones compared to just over 15 percent for Apple–roughly the same as the iPhone has now.

That report clearly sees a strong boost from Microsoft’s blockbuster deal with Nokia, which has the Finnish cell phone giant betting its smartphone future on Redmond. IDC forecasts that by 2015, Nokia’s Symbian operating system will account for just 0.2 percent of the market, compared with nearly 21 percent this year.

The market researcher also sees Android going from just under 40 percent share this year to more than 45 percent and Research In Motion dropping a bit, with 13.7 percent, down from 14.9 percent as of 2011.

In the short term, Android is clearly the big story, IDC said.

“Android is poised to take over as the leading smartphone operating system in 2011 after racing into the Number 2 position in 2010,” analyst Ramon Llamas 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.”