Google has officially announced that they will be "experimentally" rolling out the ART runtime in Android 4.4.
ART uses Ahead-of-time (AOT) compilation which promises improved app performance, and reduced strain on battery life.
The ART runtime is an alternative to the Dalvik runtime - although developers are advised to still retain Dalvik as the default for their applications to ensure compatibility across the myriad Android hardware configurations found in the wild. Google have stated that work on ART is far from complete but plans are afoot to improve its backwards-compatibilty so app developers can grasp the bull by the horns and reap the benefits of the new runtime.
We expect that more information about the future of ART will be forthcoming at Gogle I/O 2014 so stay tuned!