The Windows Store hasn’t arrived on the Xbox One just yet but you can still experience the new Emby Theater app via Microsoft Edge browser on the console. You can open tv.emby.media from the Edge browser on the Xbox One and then you get an optimised version of media centre UI on your console. It supports the Xbox One controller, AC-3 audio pass through and you get all the Emby features, including Movies, TV, Music, Live TV and Photos.
You can read more about the web based version of Emby Theater on my post from last week.
Give it a try at tv.emby.media