The next major Rainbow Six Siege expansion will be free and is slated for launch on the 5th September.
The update will bring various changes, additions and improvements including a new map and Operators. There will be two new defenders (Ela and Lesion) and one new attacker (Ying). The new map will be set in a run down theme park. The patch will also address Operation Health, capping it off to improve nagging issues with the game.
The full patch notes can be found here.