No one knows for sure when the Mythic Map Pack will drop on us outside of a Halo Wars: LE purchase.  I have heard a week after Halo Wars comes out, which is March 3 stateside and I have also heard that it comes out March 31 from a different source. Until that day, whenever it may be, here is a video of Sandbox. A new, huge, and very customizable map that people are saying is one of the best to date. Here is a link to the rest of the videos. Enjoy.