Nintendo decided to start last month's Direct show with a bang by revealing that Pyra and Mythra from Xenoblade Chronicles will be the next fighters to join the Super Smash Bros. Ultimate, but we didn't get a release date. That has, as promised, been rectified today.
Despite having to record it from his home, Masahiro Sakurai did show and explain pretty much everything we need to know about how Pyra and Mythra will fight in Super Smash Bros. Ultimate in today's stream, as well as announcing that they'll arrive tomorrow (later today if you're in the Americas.
To make it short: Mythra will be more focused on speed and beating opponents off the stage, while Pyra is all about power. We're obviously also getting a new stage called Cloud Sea of Alrest. Sakurai-san tells us to always be aware of our surroundings in this one, as Azurda will move once in a while. You can see all of this in the first video at the bottom.
The update will also include sixteen new melodies (where three are new arrangements), Monster Hunter and Ghosts 'N Goblins Mii costumes, balancing of fighters and a few other minor changes when it arrives what I'm guessing will be while those of us in Middle-Europe are sleeping tonight.