The new Save the World Pack for Chapter 3, Season 3 has been found in the game files following the v20.40 patch earlier this week.
The new 'Skatepark Royalty' Set contains the 'Toni' Outfit, 'Olli-Oop' Back Bling and 'Inline Impactor' Pickaxe. Interestingly, Epic has dropped the robot theme it's been using for cosmetics in previous STW Packs. As is the case with all cosmetic leaks, it's possible that the pack could be changed before it's released in-game. However, these items appear to be final so this is unlikely.
The release date for the new Save the World bundle is currently unknown, although it's expected to be released within the first month of Season 3.
Despite cosmetics for the new set being found in v20.40, the pack itself has yet to be added to the files; meaning it cannot be released before Chapter 3 Season 3 begins. The Mecha-Pop Pack, which is available as the current Save the World Pack in-game, will be replaced once the Skatepark Royalty items become available. These cosmetics can return to the Battle Royale Item Shop at any time in the future, although it's worth noting that the only pack to do so was Metal Team Leader; which resulted in a backlash from the community at the time.