Google has been very open about future versions of Android software recently, not only opening up the software to developers, but publicly releasing a beta so that those with compatible phones can have a play.
The aim, it seems, is to speed up the adoption of new Android versions and help squash bugs, to get around the issue that Android faces with updates. Apple, with limited hardware configurations across limited devices varieties, can issue an update across multiple models with ease, which Android cannot.
The public naming for Android P could be 20 August 2018. This date comes from Evan Blass, the Twitter leaker known as @evleaks who has a very good track record. A simple P on a calendar page suggests this will be the date that Google names and releases the software from beta.
That date works historically too. Android Oreo was named on Monday 21 August 2017, so it fits that Google would name Android P on Monday 20 August 2017.
At that time, Google will also likely release the final version of the software to begin the cycle of updates. Usually the process is that the source code is pushed to the Android Open Source Project, with over the air updates for Pixel devices following soon after.
For those expecting updates on other devices, you could then be waiting some time, as testing on manufacturer hardware and networks often takes months. We'll be keeping a track on when those updates will be arriving on your devices.
As for the name itself? There's suggestions that it's Android Pistachio, but a simple nut isn't enough for us - we think it will be something sweeter.