This was rumored late last year, after someone spoke to a CSR in a web chat -- but so far nothing. I do hope we get something, even if it's a stripped down (i.e. can't purchase from it but can play) version like iOS.
I know it's not the integration/solution that we want, but you can start the video on your iPad or iPhone and stream it to the Apple TV. I did this for all of The Man in the High Castle. A benefit of doing it this way is that you can leave the iPad on next to you, and see all the X-Ray elements on the iPad as the video plays on the Apple TV.
The lack of an Amazon app is why I own 2 Rokus instead of 2 Apple TVs. I'm a total Mac-head, and I'm totally invested in the Apple ecosystem, yet I didn't go for the TV for exactly this reason. I hope that now there is an app store, Amazon makes their own Apple TV app, but I'm not holding my breath.