Leakers have found files relating to upcoming Limited Time Modes - more specifically two.
The first mode is Gun Game, which is a play on the classic mode from other games.
Another new Game Mode
— Trix - use code “trix” (@TrixBR) February 14, 2019
"Gun Game"
"Earn eliminations to make your way through all of the weapons to the end!"
The other mode is Sword Fight, which gives multiple players the Infinity Blade through chests along with Epic weapons. Winner takes all.
"Sword Fight" LTM
— Lucas7yoshi_ // Fortnite BR News & Leaks (@lucas7yoshi_) February 14, 2019
"Treasure chests contain Epic or better weapons as well as the occasional Infinity Blade! Fight your opponents to find out who is worthy of the Blade... and who is not."