Install Android P If You're a Developer
Another reason we recommend installing the latest Android P beta is if you're a developer.
The Android P Developer Preview 5 (beta 4) contains all the final APIs and system behaviors developers will want for testing and preparation. That's because this is the last beta of Android P, Google's "release candidate" build.
If you're working on updates or making a new app, now you can test against the final API level 28. Developer documentation for Android P testing is available at Google's Android Developers site.
Basically, you'll want your apps, games or services ready the day Android 9.0 P arrives, and this is the easiest way to get a head start.