Juli Clover / MacRumors:

Apple says that public betas of iOS 15, iPadOS 15, macOS Monterey, tvOS 15, and watchOS 8 are coming in July  —  Apple is providing the new iOS 15, macOS Monterey, tvOS 15, and watchOS 8 updates to developers for testing purposes as of today, giving Apple a chance to work out initial bugs in the software.

http://www.techmeme.com/210607/p39#a210607p39