I'm of the mind that the Banjo/Dixie leak is most certainly fake, but that the Geno image post was not made by the OP of that thread. Why? Because there is literally no proof that it IS the same person, as they're all anonymous and the Geno post was not replying to the person who asked for Geno as proof. Tons of people in the same thread were posting unrelated character "leaks," so this isn't hard to imagine.
On top of that, we also DO have at least some possible evidence that the Geno post was unrelated--the guy that said it was posted 2 days prior. While there's no proof his claim is legitimate, I can't imagine why else he'd say that, other than to disprove the OP's usage of the Geno post as proof (Which appears to be the intent.) It's not conclusive, but it's still an iota more evidence for it than the idea that the Geno poster and the thread OP were the same person has.
At worst, we have no real idea who posted what, or when the Geno image was posted, which only puts us back at "inconclusive." I respect PushDustin and his work, but this in no way invalidates the image--until I see a full render or source for it, a la the Rayman leak, I prefer to believe this image could be legitimate.