Android L looks to be the biggest and most system-wide restructuring, resurfacing, and redefining update to Android in its history. Android L is the new name, though it may change by the time it makes it to users in the fall. We don't have a version number, but I don't think many of us care, given the plethora of changes outside of version numbers and easter eggs within settings menus.
L gives Android a facelift, and it looks great. The softkeys are different, using simple shapes, and a color scheme, shown off in the dialer and Gmail apps, that makes each app have its own, that looks rather nice. The biggest and most surprising reveal was the Chrome's integration with L. Previously, you had to exit out of the Chrome app on mobile to access other running/recent apps, and search within Chrome to find certain tabs you were using. With L and Chrome, each tab will now be its own 'recent task' in the switching menu/interface. Chrome, each tab of it, now is its own task, as they each technically are. And Android L treats them that way, so that's something new entirely. The new interface and look of multi-tasking is also something that's vastly different. The new recent apps button takes you to a list of apps that are shown to you like open tabs in Chrome's mobile app.
The interface is slightly similar to something that Apple slid into iOS 7's version of the Safari browser, but it is reimagined with Google at the brain center of it. The whole Android L OS looks to refresh every part of the average users' space, as well as optimizing the whole system by using the new standard ART (Android Run Time) for actually running the apps. The L update will hit all users beginning with Google's next pure Android experience, which is still unknown as of right now.
Android L will link Chrome and Android even further, and the integration announced with Chromebooks and Android notifications will further the link between not only Google's products and partners, but also a popular browser and the Android device.