Rockstar have confirmed that the second round of DLC, the Legends and Killers pack, will be available on August 10th over Xbox Live and PlayStation Network. The DLC will set you back 800MSP on Xbox Live and $9.99 on PSN, and "boasts nine new multiplayer map locations and the brand new Tomahawk projectile weapon, as well as more opportunities to earn Achievements and Trophies."
The pack also contains eight characters from Red Dead Revolver playable in multiplayer, according to the official website. There are, as reported by Rockstar themselves, still three more packs incoming, including one that's bravely carving out its very own zombie-cowboy genre niche.