This is Tower of Smash "there are unrevealed characters if you link the 3DS and Wii U versions of Smash Bros" level of mental gymnastics right here. Sakurai said we'd get every newcomer before release, and I highly doubt that when he said it he meant "we'll save a couple of characters until after we tell you we've revealed the full roster and put it in promotional material."
If Incineroar and Ken is all we get, any character after that is going to be DLC.
She technically got revealed alongside Dark Pit and Lucina, who were reclassed as echo fighters.
I try not to take sides on topics like this, but after reading your posts and watching
papagenos
video on the matter, I feel like I could add one specific point to this conversation.
We won't know what the final roster will be until Sakurai
explicitly states it himself.
No promotional material, at any point leading up to release, can be confirmed to have final base roster, unless it's produced/revealed
after that point.
If we get Incineroar and Ken revealed next, but Sakurai doesn't
explicitly state that this is the complete base roster, we can logically assume that there is at least one more character (echo or not) beyond that, which would deconfirm the specific part of the box theory about their being exactly 72 fighters (- Miis)
The box that we've seen could very well be released as is or after the suspected pair get revealed, but that doesn't necessarily mean that the box has the full roster, especially if any character gets revealed past November 2nd. The now-released card proves that promo material can have an incomplete roster.
Meaning the only way the full "box theory" will be proven true is if one newcomer + one echo between Palutena and Cloud are revealed as the final characters in the base roster more than a month before the game releases.