1980's: battle of a chip platform which left us with x86
1990's: battle of stability which got us win2K and XP
2000's: battle of hardware which finally got us hardware that can be 'fast enough' for consumer use for more than 5 years
2010's: This is the battle of the interfaces. keys/mice? touch? touchpads? leapmotion? voice? gesture/kinect? mind-control/EEG? not to mention all the assistant interfaces such as light level sensors, orientation sensors, proximity sensors, wireless connectivity such as Widi and NFC, etc.
With all the new ways to interact with technology it is no wonder OS designers are so divided with aero/desktop, metro, OS-X, iOS, Android's many faces, gnome, KDE, Unity, wii's OS, Playstation's OS, the many Car OS interfaces, etc. So far each caters to a specific interaction style while giving limited support for other forms of interaction. Hopefully by the end of the decade we will get an OS interface that will properly make use of many interaction styles without handicaping the other forms of interaction severely.