Multiple references to 120Hz support have been discovered in the tvOS 14.5 beta code. 9to5Mac believes that it could be related to the next-gen Apple TV.
120Hz Apple TVApple has seemingly added support for 120Hz output in version 14.5 of its tvOS, which will be released publicly later. - "Multiple references to “120Hz” and “supports120Hz” have been added to tvOS’ PineBoard in the latest beta release. For those unfamiliar with the matter, PineBoard is the internal name of the system that controls the Apple TV interface, similar to the SpringBoard on iPhone and iPad. These references strongly suggest that Apple is at least internally testing a 120Hz mode for Apple TV," the report said. The current Apple TV 4K box can output 4K HDR at up to 60Hz via HDMI 2.0. While 120Hz output is possible over HDMI 2.0, it will be limited to resolution under 4K. 4K HDR at 120Hz would require a switch to higher bandwidth HDMI 2.1. PlayStation 5 and Xbox Series X are the first two external players with HDMI 2.1 capabilities.
120Hz output would make the interface feel smoother. Games could also benefit. As for video, it would require content studios to move to 120fps frame rate. Today's movies are almost exclusively shot in 24fps. The upcoming tvOS 14.5 will also for the first time support both fractional and integer frame rates, i.e. both 24.000fps and 23.976fps, as reported by FlatpanelsHD The current Apple TV 4K supports 4K at up to 60Hzin February. It also adds support for the Xbox Series X and PS5's DualSense controllers. A refresh of the Apple TV hardware is long overdue. The current Apple TV 4K was launched in September 2017. Bloomberg has previously reported that an upgraded Apple TV is on track for 2021. - Source: 9to5Mac