tvOS 10.2.2 is designed for the fourth-generation Apple TV. Registered developers can download the update by connecting the Apple TV to a computer with a USB-C cable and installing the beta software using iTunes.
Because of the installation requirements, tvOS betas are only available to developers, so tvOS 10.2.2 will not be available to the public until the final version of the software is released to the public.
We don't yet know what's included in tvOS 10.2.2, but most tvOS updates to date have been minor in scale, and that's likely the case with tvOS 10.2.2 too.
tvOS 10 will soon be followed by tvOS 11, which we expect to see introduced at Apple's Worldwide Developers Conference on June 5.