Today Apple released the fourth beta of iOS 11.2, watchOS 4.2 and tvOS 11.2. Registered developers can install updates from the website Apple or 'over the air' using the Software Update mechanism.
iOS 11.2
Previous beta versions iOS 11.2 added support for Apple Pay Cash and Siri Kit for HomePod (the column will be released next year), but apart from no significant changes were found.
watchOS 4.2
watchOS 4.2 also supports Apple Pay Cash, but other than that, nothing is new. Only a new accessory icon Bluetooth has been added when playing audio, a few emoji have been changed, and overall performance has been improved.
tvOS 11.2
tvOS 11.2 brings improvements for new Apple TV 4K owners. Added automatic switching of frame rate and dynamic range depending on the displayed content. Games and other content will now look better. The new option can be found in Settings.