I never said he was 100% a character I said it was highly likely he would be.
Lucina was gonna be a costume because she was a girl, a gender swap is costume material because you get a different model with the same colors of the character.
A color of a character becoming a costume makes no sense at all.
Dark pit is just color changes to the character, no model changes at all. Why would they add all his other colors and take out that pallet?
"hey guys we're taking the dark pit pallet away from Pit so he can have it as a costume. What will this do? absolutely nothing! Dark pit costume, where you can use the other Pit colors on this dark pit costume and not know any differences!
There is 0 chance of that happening.
They took it away for a reason and its not to over glorify a specific color by calling it a costume.
Dark pit will be a character or it will be an assist trophy / intertwined with the game in a separate way.
He could be a palette swap still as well.
I said costume because Dark Pit would likely have his own name and voice and his colours would be dark while Pit's would be light, just like we saw him having at E3, which we know characters will sometimes have different voices with costumes, such as the Robins and Wii Fit Trainers, and Lucina likely would have both a voice swap and a name change when used.
They didn't technically take it away yet, we didn't see all the colour/costume options at E3, they all only had 4 costumes available, not the usual 6, there are definitely some still unseen. For instance, Skyloft Link, Lightsuit Samus, WireFrame Mac, and USA Mario weren't available to use in the Demo..nor was the mainstay Wario-Mario nor Waluigi-Luigi, the latter of which I'm fairly sure will return.
Even if you believe its unlikely, you can not, for certain, say that there is '0 chance of it happening', as the possibility is still there regardless because its something Sakurai COULD do if he wanted to, there is literally nothing stopping him from doing it, so there is at least a small chance of it being done, if not more.