I'm not so sure about that; it seems like saying that
the first wave of Smash 4 Mii costumes had Capcom costumes in it (Mega Man X and Proto Man), so that rules out all Capcom characters for Smash 4 DLC. (which wasn't the case, since we got Ryu after that)
On a similar note,
the third wave of Smash 4 Mii costumes had Fire Emblem characters in it, but that clearly didn't rule out Fire Emblem characters from becoming DLC. It seems premature to rule out entire companies and first party franchises (such as saying that all Zelda characters are ruled out because of a single Mii costume that is a generic set of armour rather than being tied to a character) based on a few Mii costumes. (or in some cases, a single Mii costume)
Ruling out specific characters, I get (it seems safe to say that we aren't getting Monster Hunter, Heihachi, Geno, Travis Touchdown, Sans, etc.), but it's odd to act like it's absolutely guaranteed that we're getting no Capcom characters because Monster Hunter and Ghosts 'n' Goblins got Mii costumes. (I don't see how that rules out Ace Attorney, Devil May Cry, Okami, Darkstalkers, Viewtiful Joe, etc. - Capcom seems to add costumes whenever they want)