Ever since I first set my eyes upon the Windows 8 Metro Start screen in June last year, I have wondered about Microsoft’s precarious balancing act between Windows 8 and Windows Phone 8. Initially, long before Microsoft unveiled Windows Phone 8, I actually thought that Windows 8 would be a smartphone operating system, too.

Of course, we now know that Microsoft has split its ecosystem with two similar, but distinct, operating systems: Windows 8 for tablets, laptops, and desktops, and Windows Phone 8 for smartphones. It turns out that I was partially right, though: Windows Phone 8 has the same core kernel and libraries as Windows 8, meaning there’s a lot of shared code between the two operating systems and that Metro apps are mostly cross-compatible. For the most part, the only real differences are the name (which is important for licensing reasons), and slightly different Start/home screens.

In recent weeks, though, I have been thinking about another possibility: What’s to stop OEMs from releasing a Windows 8 device with a smartphone form factor? Or, vice versa, a tablet device with Windows Phone 8?

While Microsoft has never officially gone on the record, the one key differentiator between Windows 8 and Windows Phone 8 is display resolution. Windows 8 Store apps will not run at resolutions below 1024×768, and to receive Windows Logo certification (official approval from Microsoft) devices must have a resolution of 1366×768. Windows Phone 8, on the other hand, supports the much lower resolution of 800×480.

Now, when Microsoft began development of Windows 8 back in 2009, these resolutions made sense. 1366×768 was (and is) the most common PC display resolution, and smartphones were still idling around the 480×320 mark. In hindsight, it probably would’ve been more sensible to draw the line of demarcation at a specific screen size, but even then, devices like the Galaxy Note have shown that it’s hard to say where smartphones end and tablets begin.

Today, of course, smartphones have almost closed the resolution gap. The current bleeding-edge phones have resolutions of around 1280×720 (six times the pixel count of the iPhone 3GS in 2009), and many laptops and netbooks are still sitting at 1366×768. There aren’t yet any 1366×768 smartphones on the market that could run Windows 8 — but really, it’s only a matter of time. Case in point: ZTE is spreading a rumor [Chinese] that it will release a 1920×1080, 5.9-inch Windows Phone 8 device next year. We’re a little bit skeptical about this one, as WP8 is meant to have a max resolution of 1280×768, but would a ZTE bigwig publicly lie about such things?

Four legs good, two legs bad

Really, if you take the physical form factor out of the equation, there is virtually no difference between Microsoft’s home-made Surface RT tablet and the latest smartphones. You could even argue that Windows Phone 8 smartphones, with its minimum requirement of a dual-core Snapdragon S4 processor, are more powerful than Windows 8 ARM tablets.

So, what’s to stop the emergence of Windows Phone 8 tablets and Windows 8 smartphones? Not a whole lot. Windows Phone 8 would probably work quite well on larger screens — and as an added bonus, the license for WP8 is cheaper than Windows 8, meaning cheaper tablets. Microsoft keeps a tight rein on Windows Phone 8, though — and considering it’s explicitly designed for the smartphone form factor, it probably wouldn’t scale gracefully to tablet screen sizes without Microsoft’s blessing (which isn’t likely to happen).

The much more interesting possibility is the possible arrival of Windows 8 smartphones. Windows 8 lacks a phone dialer, but it does support cellular networking. Presumably it would be easy enough to provide a third-party Windows 8 dialer app — but even if it isn’t, there’s always Skype. Beyond that, there’s no reason to believe that Windows 8 or RT wouldn’t work well on a smartphone. OEMs probably aren’t rushing to provide Windows RT on a smartphone — and their licensing agreements with Microsoft might physically prevent them from ever shipping a Windows RT/8 smartphone — but next year, with the arrival of Intel’s next x86 smartphone SoC (Medfield’s successor Merrifield), this might change. In 2013, there may be Merrifield-powered Android smartphones that you can root and install Windows 8 on.

Imagine if you had a pocketable device that ran full, x86 Windows. Imagine if you could plug it into a second or third display, or attach a wireless keyboard or printer, and settle down to do some work. Rather than having access to your documents on the move, you would be able to do everything on the move. You might even be able to play Crysis 3 on your smartphone. I told you, smartphones are the PCs of the future.