This week, in addition to the release of the beta version of macOS 13.3, Apple also made available a beta version of the new 16.4 firmware, which is intended for use with the Studio Display.
Over-the-air firmware upgrades are available for all types of Studio Displays. Still, this particular update is only compatible with Macs using the macOS Vista 13.3 beta. Studio Display owners running macOS Ventura 13.3 can install the firmware by going to System Settings > Software Update.
Apple has not shared any additional information regarding the contents of the software upgrade.