Developer Preview 4 of Android O was released last Monday (July 24), and it was a release candidate. Unless any major bugs are uncovered, the final version will come out soon – perhaps as soon as next week.
Perhaps we’ll even get to learn what desert it is named after – the current front runner seems to be oatmeal cookie.
Note that there’s a chance the the O release will be pushed back. Last year, Android 7.0 Nougat started to roll out to Nexus devices on August 22.