Watching the Sephiroth presentation now, since I wasn't able to watch it live due to work. It's a shame that Geno's stuck as a Mii costume again (not even with a mask that resembles his face, or a song - it's almost literally the exact same costume that was in Smash 4), and that the rest of the Mii costumes only focus on Final Fantasy 7 (where's Vivi, or a Black Mage?) Sephiroth looks neat, though - he seems slower than I expected, but given his range, I'm guessing that's for balance reasons.
Hopefully, for the music and/or spirits, we get some content from Final Fantasy games other than FF7, though I doubt that'll be the case.