Just logged into Steam, and BFG is now available for pre-order! The game will sell for $40, but if you jump in between now and the 29th, you can save 10%. According to the Steam page, the game is set for a March 2016 release.
EDIT:
To clarify, this is a pre-order. The stated benefits of preordering are:
-Getting the Space Marines as a playable faction for free (this will later be a purchasable DLC for those that don't pre-order)
-Access to the Beta test, which is due to take place a few weeks before the final release of the game.
Link:
http://www.battlefleetgothic-armada.com/shop/