A page on Electronic Arts' Origin site has leaked some details for what's included in the Battlefield 1 Season Pass. It will add four post-release DLC packs to the upcoming WWI-based shooter for $49.99, including the addition of the French and Russian armies.
The Origin page (via VG247) shows that the French army will be added in the first Battlefield 1 DLC pack, They Shall Not Pass, in March 2017. Another DLC pack will add the Russian army at a later date:
Get ready for new Operations and game modes, new Elite classes, weapons, vehicles and more. The Battlefield 1 Premium Pass includes 16 new multiplayer maps, 20 new weapons, 14 unique dog tags and 14 Battlefield 1 Battlepacks containing stand-out weapon skins. Each Battlepack is delivered monthly, starting November 2016.
Season Pass subscribers will get access to each DLC pack two weeks before they are released for all of the game's players. Battlefield 1 will be released on October 21 for the PC, Xbox One and PlayStation 4.