According to a support document, firmware version 5A374 adds features and capabilities for the new wireless earbuds.
Version 5A374 release notes
● Added features and capabilities to support the new AirPods Pro (2nd generation)
AirPods Pro 2 feature numerous enhancements including richer audio, next-level Active Noise Cancellation, Adaptive Transparency, personalized Spatial Audio, touch control, longer battery life, and more.
You can learn more about the differences between AirPods 3 and AirPods Pro 2 here:
● AirPods 3 vs AirPods Pro 2
Check out some early reviews here:
● AirPods Pro 2 Review Roundup [Video]
Notably, Amazon currently has AirPods Pro 2 on sale for $239.99, down from Apple's price of $249. Additionally, they are still listing a September 23 release date.