YouTube says that the feature will be implemented in November and will be a part of many updates planned for YouTube viewing on mobile devices.
This upcoming feature will allow people to add videos to their device to watch for a short period when an Internet connection is unavailable. So your fans’ ability to enjoy your videos no longer has to be interrupted by something as commonplace as a morning commute. [...]YouTube's iOS app was last updated late last month with continuous, touch-free playback of video playlists and a new picture-in-picture playback that allowed users to watch a video while still browsing through search results. The service originally launched a native YouTube app for the iPhone after Apple removed the Apple-supplied YouTube iOS app with the release of iOS 6.
Check out the YouTube blog when this launches in November for more details on how this will work for viewers.
YouTube is a universal app for iOS devices and can be downloaded from the App Store. [Direct Link]