Season 2 (TBD)
While the video doesn't tell us when Part II is coming, at least we know The OA has been picked up for a second season. We don't know when, though I'd guess late 2017.
Having been missing seven years, Prairie Johnson mysteriously returns, blind when she went missing now she can see. The events unfold over eight chapters. It appears she had a near death experience, and marketing has made reference to "the light" and "the dark."