Research analysts IDC predict Windows Phone 7 worldwide sales will beat iOS devices by 2015.

IDC claims the worldwide smartphone market will grow 49.2% in 2011 as more consumers and businesses turn to smartphones. “Smartphone vendors will ship more than 450 million smartphones in 2011 compared to the 303.4 million units shipped in 2010,” says IDC.

“Overall market growth in 2010 was exceptional,” said Kevin Restivo, senior research analyst with IDC’s Worldwide Quarterly Mobile Phone Tracker. “Last year’s high market growth was due in part to pent-up demand from a challenging 2009, when many buyers held off on mobile phone purchases. The expected market growth for 2011, while still notable, will taper off somewhat from what we saw in 2010.” IDC also believes Android will take over as the leading worldwide smartphone OS in 2011 after taking the number 2 position in 2010.

Perhaps the biggest news is that by 2015, IDC predicts Windows Phone 7 will account for over 20% market share, above iOS’s 15%. The prediction is based on the significant implications of the recent Nokia and Microsoft deal. “Up until the launch of Windows Phone 7 last year, Microsoft has steadily lost market share while other operating systems have brought forth new and appealing experiences,” added Llamas. “The new alliance brings together Nokia’s hardware capabilities and Windows Phone’s differentiated platform. We expect the first devices to launch in 2012. By 2015, IDC expects Windows Phone to be number 2 operating system worldwide behind Android.”

Nokia said recently that it plans to ship Windows Phone branded devices to developers when they are available later this year. Nokia is currently engineering Windows Phone devices and is expected to wait for “Mango”, the next version of Windows Phone, until it unveils them later this year. “Mango”, the codename for what will likely be named Windows Phone 7.5, is currently in the early beta stages at Microsoft. The software giant revealed a number of new features in February that will ship as part of its Windows Phone point release later this year. Nokia is reportedly waiting for multitasking, IE9 mobile and others before it releases its first Windows Phone device.