I don't think it's the copyright info that seals Snake's fate, it's the fact that he's not visually represented on the back of the box along with the other third-party characters.
The writing's just on the wall. There is literally no reason they would hide Snake this long, especially when (a) Sonic was revealed almost a year ago now and (b) history tells us that Nintendo uses third-party characters on the box to sell the game.
I mean, if Sonic wasn't already long announced, that'd be one thing. But everything just doesn't add up; there's no logical reason Nintendo wouldn't use Snake to promote the game along with Sonic, Mega Man, and Pac-Man.
At least for me personally, I now feel 100% sure Snake is cut. If that's accurate, I won't really miss him that much (love the character but didn't really care about him in Smash one way or the other), but I will miss his Codec conversations and I feel pretty bad for all the Snake fans out there.