It appears that next week we will have an open beta of Halo Wars 2, to coincide with E3:
http://www.mondoxbox.com/en/news/55206/ ... to-20.html
In addition, some screens of gameplay have begun to show up on reddit, like:
And a few more in this gallery:
http://imgur.com/a/Jsd1A
Feel free to add more info -- if I see anything else I shall post.