Later today Halo Wars will become backwards compatible and show us as ‘ready to install’ for those enrolled in the Xbox One Preview program, no dates mentioned on when it will roll out to everyone. Sounds like they want to do a little testing before it gets a full release.
Source: Windows Central / Major Nelson
Info on the Preview Program
Very good news. I’ve been waiting a long time for this.
Excellent. Progress is happening.
Yeah, playing tonight!!!
I am still waiting for it to show up. Has anyone been able to download it yet (I am a preview member)
I am downloading it right now.
10: 45 Mountain Time [-7], Canada.
I have the preview dashboard which I think is also the program and halo wars does not show up ready to install
Can’t express how much I envy the lucky preview users right now…
Any clue on when it will be available to everyone?
i can’t wait to go home and download it!!!
This here is the best news I’ve heard in days
YAY!
> 2535435176560939;7:
> I have the preview dashboard which I think is also the program and halo wars does not show up ready to install
Same. I cannot find it anywhere…
It will only show up if you have the game on digital, if you have a physical copy and your in the preview program you will need to insert the disc.
On a other note, the game plays fantastic and just how I remember it, you get the FPS drop when there is a huge battle taking place but other than that it is 100% amazing already but around 6 hours into it since it became available again!
I think I de enrolled from the preview program 
waaagghhh lol
GT is berd41 message me if you want to play halowars.
Someone wanna invite me to the preview program have been waiting so long for this