Android 5.0, aka Jelly Bean, rumored for Q3 release

The next iteration of Android is looking to launch in June, just as Ice Cream Sandwich, the current version, finds itself on more devices.

Although Google is activating nearly 1 million Android devices per day, Android is often cited for device fragmentation. And there's credence to that criticism. There are devices being manufactured at this instant with versions of Android that are nearly 2 years old.
The reason this happens is because manufacturers often saddle devices with tweaks to the Android OS, such as custom overlays, apps, and widgets, that change the Android experience. When this route is taken, it typically takes the original manufacturer months to update its customizations to the latest version of Android--if the device gets updated at all.
Google Nexus devices are an exception to this practice. Devices like the Galaxy Nexus come with an unaltered installation of Android, giving users the default experience of the OS.

 

Source:CNET