The XDA has gotten its hands on what appears to be the most recent beta for Android 9.0 (Pie) on the Samsung Galaxy S9. This build does not exactly introduce new features, but is reported to have fixed the significant bugs of the previous beta. They include failing navigation gestures and incomplete native night theme.
https://www.notebookcheck.net/Latest-Android-Pie-beta-for-Galaxy-S9-reported-to-have-working-night-theme-and-gestures.345966.0.html