CIO — Try as it will to break through in the mobile space, Microsoft is still struggling to gain any ground with Windows Phone almost a year and a half after its launch.

Things have gotten so bad that that in a recent market share report by research firm Nielsen, Windows Phone market share was so small in the U.S. that Nielsen didn't even bother to break out its usage. It was relegated to the dreaded "other" category.

Well at least there's the dominant Windows client OS, right?

Right?

As a PC operating system, Windows has been dominant for decades. But there's a palpable change in the air. The post-PC world is becoming the real world, transforming before our eyes in homes, at airports and in office towers.

Connected mobile devices — basically smartphones and tablets running Apple iOS and Google Android — are quickly encroaching Windows PCs coveted space.

A new report from research firm IDC gives credence to the post-PC worldview.

New smart-connected devices shipped out to consumers and businesses are expected to exceed 1.1 billion units in 2012 and will reach 1.84 billion units by 2016 — which is twice the current ship rate of 2011, according to the research firm.

The report's conclusion is that Windows on x86-compatible chips — i.e. PCs — will take a big hit between now and 2016, and Android OS will rise in power in the same time period. While the amount of Windows PC shipments will grow slightly between now and 2016, the PC's share of all devices shipped will decrease by almost 11 percent.

From the IDC press release:

"IDC expects a relatively dramatic shift between 2011 and 2016, with the once-dominant Windows on x86 platform slipping from a leading 35.9 percent share in 2011 down to 25.1 percent in 2016."

"The number of Android-based devices running on ARM CPUs, on the other hand, will grow modestly from 29.4 percent share in 2011 to a market-leading 31.1 percent share in 2016. Meanwhile, iOS-based devices will grow from 14.6 percent share in 2011 to 17.3 percent in 2016."

Windows across all devices, at least according to IDC, will get bypassed by Android in four years and will lose ground to Apple iOS. In short, we are not too far from tablet and smartphones being the world's dominant devices, as Windows-based PCs fall further into the background.

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What should be most disturbing for Microsoft is that the IDC report assumes Windows 8 tablets (Windows on ARM) and Windows Phone will have little affect over the next four years.