Apple has released the fifth developer betas for iOS 12.1, tvOS 12.1, and watchOS 5.1 today, introducing no major feature additions except for a slew of improvements and bug fixes.
Tvos 12.1 RSS
The fourth developer beta builds for iOS 12.1, watchOS 5.1, and tvOS 12.1 include only a few minor updates generally. The betas are now available from Apple's developer center or via OTA.
Apple is releasing the first public beta builds for iOS 12.1 and tvOS 12.1 today; however, if you're buying an iPhone Xs this week, you might want to skip it, as there's no image for the device yet.
Apple today released the first betas for the first minor updates that follow this week's major updates. You can now test out iOS 12.1, watchOS 5.1, and tvOS 12.1- if you're a developer.