Revealed on the Super Smash Bros. DLC page were the next batch of Super Smash Bros. Wii U/3DS DLC content. It was slated for release on the 30th of September and will include some familiar stages/costumes.
The video that was show on the page and is unlisted on the Super Smash Bros. Youtube channel shows off brand new costumes for the Mii Fighter based on Captain Falcon, Toads, Fox McCloud, Viridi and the Rathalos and Hunter armor set from Monster Hunter. On top of that are sets of executive business suit costumes to make your Mii look fancy.
For stages: It was announced that there will be a Super Mario Maker stage that will be different every time you play the map and actively changes as you fight on the stage. Further more, there will be the return of the Great Sea stage from Brawl where combatants fight on a boat that traverses the Great Sea once again. The Great Sea stage will only be available for the Wii U version. The Mario Maker stage is available for both games.
The DLC will be available to purchase right now. You can pick up the entire bundle including the mentioned stages with the costumes for $13.53 on both platforms, $7.74 for 3DS only or $9.73 for the Wii U only. Otherwise you can each costume for 75c each ($1.15 for both platforms), the Great Sea stage for $1.99 and the Mario Maker stage for $2.49 ($3.49 for both platforms).