Following the announcement of Byleth, the fifth and final character as a part of the Fighters Pass, Super Smash Bros. Ultimate director Masahiro Sakurai announced that even more downloadable content is on the way. As such, Sakurai announced Fighters Pass Vol. 2.
No additional details were available about the contents of the newly announced second Fighters Pass, but Sakurai said all the characters have already been decided. Those who purchase Fighters Pass Vol. 2 will also get The Ancient Soldier costume for Mii Swordfighter from Legend of Zelda: Breath of the Wild. More details will emerge in the future.
Source: Game Informer Second Fighters Pass To Bring Six More Characters To Super Smash Bros. Ultimate