The Apple TV 4K will eventually support Dolby Atmos
https://www.theverge.com/circuitbreaker/2017/9/21/16345126/apple-tv-4k-dolby-atmos-support-coming
The reviews are out for the new Apple TV 4K, and while the box is priced as a luxury product, it doesn't yet support the highest-quality AV standards. The new Apple TV, as The Verge's editor-in-chief Nilay Patel reports, isn't yet compatible with the Dolby Atmos surround sound format, a must-have for modern home theater setups. Apple confirmed to The Verge, however, that it'll eventually support Atmos, although it didn't provide a timeline.
You should read Nilay's full review because he explains the joys of Atmos and the letdown that is Apple neglecting to support it at launch. What's particularly befuddling about the company's omission is that Atmos is supported by other, cheaper set-top boxes. The cheapest Roku players support it, as does the Xbox One S. If you're an Atmos fan, the Apple TV 4K isn't going to satisfy you just yet, but there's hope.