Google just released the Android 9.0 P Developer Preview 4. According to Google's release schedule, this is the candidate builds which includes the final APIs and near-final system images for development and testing.
The Android P Developer Preview 4 is available to the Google Pixel, Pixel XL, Pixel 2, and Pixel 2 XL. If you want to get a taste, you have a bunch of options. You can either flash Preview 4 Images or OTAs, or just sign-up for the Android Beta and wait for the OTA update.
Here's a link to sign-up for the Android Beta program.You can also grab the new Android P DP4 images here and OTA files here.
Android P Developer Preview 4 should be the most stable version available right now. This release is version PPP4.180612.004 for all four phones.
Here's a link to sign-up for the Android Beta program.You can also grab the new Android P DP4 images here and OTA files here.