The Fortnite creators on the 11th of May added into the game code lines that indicate that PvE-mode Daybreak will be coming soon.
Also, the legal documents leaked from the Epic Games vs Apple issues, revealed it, because some of the iPhone’s owners had a trial version.
The plot is that the player wakes up on the shore of the island unarmed and doesn’t remember how he got there. The quest is to survive solo or with the help of other players and repair a helicopter to fly from there in three days before a storm arrives.
The PvE-mode was in Fortnite earlier. Initially, there was only it in the game, long before the most popular of “battle royale” appeared.