Kind of wanted to comment on a common rumor that I've seen on here and Discord about 6 being "Dante or Dante like character" and one description even describing it as a "Joker echo." For starters, Dante is pretty damn distinct. White hair. Red coat. Shirtless. Fights with a broad sword and guns. It would be virtually impossible to mistake him for anyone else.
This is why my theory is that this is someone in early development. Dante is too unique to be mixed up with anyone else. If it really is Dante, it's the super early stages of the character. Either way, there's no way they're 6. If Dante was next, he's one of those characters that you could recognize from across the room. Way too many distinct design choices to have him mistaken for anyone else, especially if these rumors are supposedly coming from playtesters.
Back in 2018, we had 4Chan leaks of Plant in August. This means Plant was roughly 6 months from release and STILL done enough to be recognized. Even if Dante was an E3 reveal and still couldn't be recognized on sight, that's not a good sign. The sheer ambiguity of this mystery makes me believe, no matter who they are, they are nowhere close to completion and more than likely not 6.
But yeah, it could be the most Sakurai pick ever when only the guy himself knows who it could be. For all we know it'd be Rooks from Arcana on the SNES, or something.