No, that’s not a typo. Analysts at IDC are now forecasting that the Windows Phone mobile operating system will be the number two smartphone platform by 2015. And Android will be number one. “Android is poised to take over as the leading smartphone operating system in 2011 after racing into the number two spot in 2010,” says senior researcher Ramon Llamas. But it’s Nokia’s recent shift from Symbian to Windows Phone that will have the biggest impact on the market going forward, Llamas believes.

Android #1, Windows Phone #2

By 2015, IDC projects that Windows Phone 7 will have an install base of 20.7% of smartphones, behind Android at 45.4%. iOS will be in third place at 15.3% and RIM’s BlackBerry will be at just 13.7%. Symbian, meanwhile, will have fallen to just 0.2% of smartphones worldwide, IDC says.

In the near-term, Android will power 39.5% of smartphones by the end of 2011, while Symbian drops to 20.9% by year-end, IDC says. Apple’s iOS will be at 15.7%, RIM at 14.9% and Windows Mobile/Windows Phone 7 will be at 5.5% in terms of smartphone market share.

Overall, the worldwide smartphone market is expected to grow 49.2% in 2011, with smartphone vendors shipping 450 million units this year, up from the 303.4 million units shipped in 2010. The smartphone market will grow more than four times faster than the overall mobile phone markets, notes IDC.

Are You Buying This?

ZDNet’s Matthew Miller hesitates to believe these 3-year forecasts, considering the rapid changes seen in the mobile industry today. “Microsoft and Nokia could break up if things don’t work out,” he remarks.

Engadget’s Vlad Savov questions the numbers, too, reminding readers that IDC’s forecasts haven’t always been accurate. “While the new prediction sounds very reasonable today, four years of unknown unknowns is a mighty long time to try and forecast,” writes Savov.  “We have a feeling we’ll be looking back and chuckling at this within a few short months,” he says.

In addition, we have to point out a minor inaccuracy on IDC’s part. “Windows Phone 7” is not what Nokia is calling the OS on its own hardware. “We were deliberate about using just ‘Windows Phone’ so as to not specify any version of that platform,” Nokia PR rep Karen Lachtanski told us recently. “That wording is agreed upon between the two companies.”

We suppose that might be splitting hairs when it comes to market share numbers, but we thought it was worth a mention.