https://www.techradar.com/news/latest-fortnite-update-delayed-on-nintendo-switch

While Fortnite players on all the other platforms will be receiving a client update “to improve stability” by August 28, those who play on Nintendo Switch aren’t so lucky. 

Epic Games has announced via Twitter that it has delayed the Switch update because it needs extra time to work on matchmaking tweaks, which will apparently be arriving with the patch when it’s released. However, a specific date for that hasn't yet been revealed.