Apple has already released the first developer betas for iOS 12.1, tvOS 12.1, and watchOS 5.1, barely 24 hours after the public releases of iOS 12, tvOS 12, and watchOS 5. With this new round of betas, Apple appears to have moved its release notes into an HTML web page, rather than the PDF versions that have been the norm for the past several years, although all three versions note that “There are no notes or known issues for this software update” although 9to5Mac notes that group FaceTime appears to have returned — a feature that was promised for iOS 12 but pushed to a later version.
iOS 12.1 may also add dual-SIM support for the new iPhone models, although there is currently no evidence of that, and in fact there are currently no restore images available for the iPhone XS or iPhone XS Max, so anybody planning on upgrading to one of the new models may want to avoid installing the new betas for now, as it won’t be possible to restore an iCloud or iTunes backup made with iOS 12.1 onto an iPhone running iOS 12; a similar situation occurred last year with iOS 11.2 and the iPhone X, although Apple was quick to release an iOS 11.2 restore image later the same day as the iPhone X was released. Whether or not that will be the case this year remains to be seen.