Google's Android P Developer Preview Beta 4 is available now if you have a Google Pixel, Google Pixel XL, Google Pixel 2, Google Pixel 2 XL, and Essential PH-1. Today Google has announced Android P Beta 4, an early release candidate build which comes with near final system behaviors.
The official Android P APIs have been finalized with the previous Android P Beta and Android P Beta 4 seems to be all about bug fixes and minor improvements. No major new features have been added in the newest Android P Beta, Google keeps on polishing the software ahead of its graduation from beta to stable which is said the released in August or September.
System images are up for grabs if you want to manually flash your Pixel's or Essential PH-1. If you've been running Android P Beta 2 on your device you'll see an over the air update notification in the next few days. If you haven't joined Google's Android Beta Program and want to do so now head on over to the Android P Beta source link below. Once you enroll a supported device you'll receive an OTA update that will install the latest beta.
Source: Android Beta Program, Essential PH-1 Developer Beta