MondoXbox spotted a product page on the Xbox One website that featured the game, and with it came beta news that we probably were not supposed to see!
According to the page the beta will begin Monday June 13th. This means the news was probably set to be revealed during the Xbox E3 Press conference that day, and the game could be playable on the showfloor.
The beta will then last until June 20. We are not sure if this is only Xbox One, or will also include PC. We are also unsure what type of content to expect.
According to other details though, the beta will come in at 13GB.
Halo Wars 2 is in development by Creative Assembly and will release on both Xbox One and PC via the Windows Store. It has not been noted if the game will see cross platform support between the two.
Expect more details at Microsoft E3 Conference being held this Monday at 9:30AM.