https://www.gamespot.com/articles/this-is-when-fortnites-540-content-update-drops/1100-6461677/

Season 5 of Fortnite is drawing to a close very soon, but before this season officially wraps up, developer Epic has some new content in store for the popular battle royale game. The studio announced on Twitter that it will roll out Fortnite's 5.40 content update across all platforms tomorrow, September 11, at 5 AM PT / 8 AM ET / 1 PM BST, and it looks set to introduce another new gun to the game. [Update] Epic has completed a client update for Fortnite, and the full patch details are expected later today.

Epic hasn't formally confirmed what new item will arrive as part of the 5.40 content update, but it will presumably be the Suppressed Assault Rifle, which Fortnite's in-game News feed teases is "coming soon" to the game. According to its accompanying description, the new gun is a "silenced weapon that rewards precision aiming."