There are numerous Operating Systems for desktop use, Windows 7 & 8, Mac OS, various versions of Linux and more. Android is currently a Mobile Device Operating System competing with the likes of Apple's iOS and Window phones.
Take a closer look at Android though and you'll see that underneath its mobile device skin, there is potentially an Operating System that could be used on a Desktop PC. It already does everything a PC can, and the advent of Android gaming consoles such as the Ouya shows that Android is more than capable of being shown on larger screens.
Imagine a world where your desktop OS and mobile phone was identical... oh yes, Ubuntu have already done that! So there's no reason at all why Android 4.4 KitKat could not be used on a desktop environment.
Let's think about this. Productivity suites such as Microsoft Office, these can be done with Google's very own Documents, so that would work perfectly. Music and video players, these work perfectly in Android so again no problem on a laptop. Then there's downloading things from the internet, again, Android is more than capable with even Torrent clients being simple to use.
As a web browser, Chrome works perfectly on an Android machine, and if you're not a fan of a Google browser or product then there are plenty of alternatives. As for storage, we all know you can easily attach a USB drive to your mobile device, so again there's no problem at all and Android can cope admirably.
So, what's stopping Google releasing Android as a desktop Operating System? It's not even as if Android needs huge specifications on a machine to run. Simple answer is, I have no idea, but I believe in the coming years Google will release an Operating System. They already have Google Chrome OS which works on Chromebooks, surely with a few tweaks it would be easy enough to get a complete Android system working.
There are USB stick based mini-computers that actually run Android on your TV. These work usually with Android version 4.0 or so using very low spec chips. They are basic, but prove that it is indeed possible for this mobile OS to work on a big screen.
How many years until Google release Android as a desktop OS? Let's just hope it's in the pipeline because potentially it'll be an Operating System that anyone can just pick up and use.