The leak comes from the usually reliable fortnite insider, shiinabr (via insider gaming) Fortnite creator shiina confirmed the spongebob collab, including details of potential cosmetics including plankton wheels, jellyfish boost, and flowers drift trail. According to shiina, uefn users will soon have the option to include paid random items in their experiences
Find Out About The Fortnite Leaks From Shiina - The Nature Hero
According to the fortnite leaker shiinabr, the next major phase of the storyline could be created using uefn (unreal editor for fortnite)
This would be a shift in how seasonal content is created.