Android 8 'O' releases on Monday 21 August
Developers and keen beta testers have been able to download Android O for several months now, and the less keen-to-be-testers have had sources such as Marques Brownlee/MKBHD to visit and watch 4K videos showing off key new features.
However, earlier today the Android website was updated with an "eclipse" page proclaiming that "Android O is touching down to Earth with the total solar eclipse, bringing some super (sweet) new powers!" This is accompanied by a countdown timer and the line "...when you'll meet the next release of Android...revealed via livestream from New York City at 2:40 PM ET."
Google appears to be making the event very eclipse centric (maybe subtle messaging about Android O 'eclipsing' the competition or its previous versions?), so those wanting to know more about how to watch the reveal event or information on the eclipse should head on over to the Android Eclipse page.