It looks like Google's next upgrade of Android is Android 5.1 and will be shipping soon on Android One devices to Indonesia. The new version is still Lollipop, but it has been spotted and confirmed to be shipping out on new Android One phones in that area of the world.
It's odd that Google would jump straight from 5.0.2 to 5.1, but perhaps there is a method to their madness. The folks at Android Police got their hands on a number of pictures of the Android One with the 5.1 version of Lollipop running. We have a number of pictures from them in the thread below.