Super Smash Bros. Ultimate downloadable content will be launched early next year, and they will consist of more than the previously announced passport collection for fighters. Nintendo's support site states that Mii Fighter costumes will also be included in the mix, sold separately from the larger downloadable content pack.
These 75-cent purchases include a single costume for the game's Mii Fighters that are customizable by the players design from head to toe. There are already many costumes that you can purchase and collect during the game, from unique headwear to outfits based on existing characters. But just like Super Smash Bros. for Wii U before that, the Ultimate catalog clearly has room for extensions.
The DLC will be available next year; Appointments remain as indefinite as the number and style of the costumes. For comparison, the previous smash game had six new Mii Fighter outfits with a total of 42 pieces.
We have contacted Nintendo for more details and will update the update accordingly.