Yes, but what character?
The problem is that people are jumping to the conclusion that we'd get Doomguy and/or Geno. There's still a possibility that there's also a Doomguy costume. There's still a possibility that there's a boatload of Bethesda ones and it releases alongside an Elder Scrolls rep or something.
Imagine if Tails or the Teddie hat leaked before Joker's reveal? That doesn't confirm Eggman or Yu, but people might've assumed so.
Yeah and I'm not discounting that possibility, I'm just pointing out the comparison isn't a fair one to make.
If you want my personal opinion, this would be the equivalent of if the Chocobo mii costume from Final Fantasy leaked.
It would be
possible that that would merely be indicative of more FF costumes on the way or another SE character, but really it's far more likely it's a character, except instead of a huge pool of characters, there's really only 3 possible characters (Doomguy, Falloutguy, Dovahkiin) and I'd obviously lean more on the series we
know is represented.
So, until I see a return of the Geno costume or the Doomguy Helmet mii hat (or any Bethesda-owned character), I'm going to
lean on it being that Doomguy is in.