Just a little more info: Ark will release 16th (most likely 0:00) of your own time zone. Microsoft handles the release and its set like that. So once its 16th in your country, you should be able to get it. Im kinda fortunate because 16th will be in just 10 hours (yaay!) .
Yes, some people already have it on Xbox because they are streamers / youtubers (somebody mentioned Draax, <S ). They gave them copies to advertise the game before it launches, you still have to wait.
Also, the game isnt on the shop ATM (as far as I know, or at least not for me) because it shows only games that