Of all the places we expected to hear about new Halo Wars maps, we didn't think it would be within the game itself. If you're very, very patient -- seriously, it takes around half an hour -- the information crawl that scrolls across the bottom of the main menu will show the names of three upcoming maps. The crawl also mentions the recently revealed gameplay modes from the upcoming "Strategic" Options DLC. The three maps mentioned are Barrens (1v1), Blood River (1v1) and Memorial Basin (2v2).
We've contacted Microsoft to see if the maps will be part of the upcoming DLC or if they are intended for a separate release. If you're still not convinced, you can check out some shots we snapped of the map names in the gallery below.