Driven by Nokia's stronghold in emerging markets.
This is a bold projection from IDC, given that the WinPho's share currently sits at just 5.2 per cent, while iOS is on 20.5 per cent.
It says these shares are due to change respectively to 19.2 per cent and 19 per cent in the next five years.
So the WinPho lead will be very slight, but it's still a lead, and it's important for fledgling Nokia, as its devices in emerging markets are set to drive the share increase.
What makes it even more audacious is that the first tranche of Nokia Lumia devices has not been an overwhelming success, and the firm is still focused on Symbian in developing markets.
IDC reckons Android will continue to dominate the market, although its share will fall from 61 per cent to 52.9 per cent, while BlackBerry will have a minimal loss from six per cent to 5.9 per cent.
The overall mobile phone market is set to grow by four per cent year-on-year, which is its lowest CAGR since 2009, as economic conditions and falling feature phone sales take their toll.
That said, feature phones will still account for 61.6 per cent of sales this year.
Kevin Restivo, senior research analyst with IDC's Worldwide Quarterly Mobile Phone Tracker, said: "The smartphone parade won’t be as lively this year as it has been in past. The mobile phone user transition from feature phones to smartphones will continue in a gradual but unabated fashion."
Ramon Llamas, senior research analyst with IDC's Mobile Phone Technology and Trends team, said: "Underpinning the smartphone market is the constantly shifting OS landscape. Android will maintain leadership throughout our forecast, while others will gain more mobile operator partnerships (Apple) or currently find themselves in the midst of a major transition (BlackBerry and Windows Phone/Windows Mobile).
"What remains to be seen is how these different operating systems – as well as others – will define and shape the user experience beyond what we see today in order to attract new customers and encourage replacements."