https://www.pcgamer.com/map-updates-suggest-fortnites-next-season-might-begin-with-a-rocket-launch/

Fortnite's Season Four is coming close to its finish, and clues pointing at the theme for Season Five have already started appearing. First there was a skull logo that began showing up on all the in-game televisions, and which resembled the villain's lair, a new location near Snobby Shores. Inside the villain's lair there's a rocket, and a new holographic display suggests that it's nearing launch.

Currently the leading theory among players is that the Visitor, the character seen on the loading screen above, has been gathering hop rocks as fuel and is planning to use that rocket to blow up Moisty Mire. Or maybe people are just looking for an excuse to suggest that Moisty Mire is going to get bombed into a crater and then renamed.