The two new codices will revolves around the xenos and Imperial armies. Few details were shared beyond the redacted covers (see gallery below). GW also revealed the new Black Templars Codex Supplement coming in November. This supplement brings rules for reinforcements to help the Emperor's Champion strike fear into the hearts of his enemies on the battlefield.
Games Workshop also announced Hexfire, a new battlebox for Warhammer 40,000, and two new Codices (see "'Warhammer 40,000' Battlebox").
Click on Gallery below for full-size images!