In less than a week, Rockstar is releasing the completely free of charge DLC, Outlaws to the End. This DLC will bring more missions for you to play along with your friends in multiplayer mode. They've already released some info on the missions, and recently released even more info on two new missions, The Herd and The Escape.
In The Herd, you're guiding cattle home to Armadillo while defending them from rustlers, while The Escape is an action-packed mission where you get to use the gattling gun! Awesome! Read more about the two missions on their respective pages on the wiki.
Source: Rockstargames.com