The chaos is already underway in Fortnite Season 3. Meteors are bombarding and raining heavily from the sky causing a shower of destruction everywhere players go. See this video for the chaos.
In the first message tweeted earlier, fans were told to "Battle. Adapt. Win." while accompanying an image of a superhero-like figure. The same image along with the words "Brace for impact!" was posted on Fortnite's website suggesting that the new skins and bling for Season 4 could be hero or villain themed after some kind of huge destructive event. The second tweet "Fight with Honor." re-enforces this idea. The third message "check every corner, box, and bush" was a slight divergent from the superhero theme but possibly is clue as to how a player might superhero or supervillain powers perhaps with a smooth integration into Season 3 gameplay. The fourth message was a little mysterious where fans were told to "Leave your mark."
The fifth message is finally out, and fans of Fortnite Battle Royale were once again told to "Brace for Impact!" possibly implying a huge meteor impact signaling the end of Season 3 and a new beginning in Season 4 where superheroes and supervillains will battle it out. Season 4 coming out May 1, 2018!!