From what I can dig up on the forum, it should be out soon but there doesn't seem to be a definite date right now.  It sounds like RebelMike (the man behind the game) is being kept quite busy with his real job at the moment but hopefully he can give us an update soon.

I'm planning on venturing into 15mm fantasy in a big way soon. I own several boxes of the Mighty Armies miniatures plus many figures from other manufactures. The Mighty Armies rules really appeal to me and I'm anxiously awaiting the new expanded rules. The build your own feature is important in a fantasy rules set.

I'm also looking at HoTT which is a widely played set with a differern basing system. I would like to commit soon. When can we expect the new Mighty Armies???