While the page doesn't mention which phones are getting the update first, we can easily assume that the Google Pixel lineup - like the Google Pixel 3, Google Pixel 3XL, and Google Pixel 3a phones - will get it on launch day, as has been the case with prior major Android releases.
#Android10 is here 🎉 and ready to help. Full of new and familiar features, Android is more inclusive, accessible and safer than ever. pic.twitter.com/uszOlbGm6PSeptember 3, 2019
The page does list everything new in Android 10, including Dark theme, which you toggle on and off in the page itself to see how it will look in the screen demos of other new features. Most, but not all first-party Google apps work with dark mode today, though some like Gmail won't support it until later in September, according to The Verge (opens in new tab).
Those include Focus Mode, which blocks out most notifications, and Gesture Navigation, to get around the phone without triple buttons, bottom bars, or side-swipes. And, of course, more privacy controls, as well as Project Mainline, which enables over-the-air security updates that beamed to your device automatically between major Android releases.
Other quality-of-life features listed on the Android 10 page include Live Caption, which we saw first at Google IO back in May that captioned streaming audio and video in real time. Sadly, that won't launch until later in 2019 and will only be available for Pixel phones, at least at first.