Apple has released first public betas of macOS Big Sur, iOS 14, iPadOS 14, tvOS 14, and watchOS 7. The completed (ie, non-beta versions) should arrive this fall.
The public betas are available on Apple’s Beta Software Program website. Just remember that beta software, so proceed with care. Apple does public betas in order to increase the size of the pool of testers. The tech giant recommends keeping back-ups of your files before installing a public beta.