Future YouTube update for Android will bring background audio support10
What was found in version 5.2.27 for Google Play is that the update is a yawner. But taking apart the APK found that here will be an upcoming feature that will give support for background audio. This means that you will be able to start a video on YouTube, switch to another app, or even turn off the screen, and continue to hear the audio from the YouTube video. Unfortunately, this feature is also not part of the update to version 5.2.27.
While the offline video playback is not part of the current update, some code strings suggest that it will be part of an update coming soon. Now YouTube fans sporting an Android powered device have twice the reasons to keep looking out for the next YouTube update for Android.
source: AndroidPolice via AndroidAuthority