Preview at WWDC likely in June, followed by September launch.
Apple's Live Photos Take Up About 2x Space of Normal Images
A still photo captures an instant frozen in time. With Live Photos, you can turn those instants into unforgettable living memories. At the heart of a Live Photo is a beautiful 12‑megapixel photo. But together with that photo are the moments just before and after it was taken, captured with movement and soundLive Photos will be viewable on existing iPhones, iPads, Macs and Apple Watch devices with the latest operating systems. Apple is also opening up the API for developers to support the new format in their own apps. Facebook has already committed to supporting Live Photos in their iOS app later this year.
While few details about the new image format has been released, TechCrunch's Matthew Panzarino reveals in a video that the new format will take up approximate twice the space of a normal 12MP photo. Panzarino describes that even the current iPhones start taking photos the moment the Camera app is launched, and that traditionally, only the last photo the moment the shutter is pressed is stored. The new system will simply take the surrounding photos and compress them into this new format.
Meanwhile, @DanMatte reveals that the new Live Photos format is a bundle of images based on the JPEG file format, allowing them to be easily sent as a still image to devices that don't support Live Photo. Apple's developer documents indicate that you can share the image as a regular JPEG if desired.
More details should come out as the new iPhones begin shipping on September 25th.