No chance. Fortnite wasn't anywhere near it's peak when the DLC was being decided (The interview about Steve suggests that most if not all of fighter pack 2 are left overs from the suggestions Nintendo gave Sakurai for fighter pass 1) And fortnite is passed it's peak now. Popular, sure, but not setting the world on fire like it had. With all the characters on the table, Nintendo wouldn't suggest a character from a flash in the pan game, that doesn't have a definitive main character and only got popular because of one of it's side games that overshadowed the actual game.
Like with all things said from developers, you can't take it to mean much one way or the other. Yes, if they do have a character in, they can't reveal it so a "no comment" could be appropriate, but look at how suspicious that looks? The better thing would be to deflect like Grant Kirkhope. He didn't lie and say B&K weren't in, nor did he break NDA and say they were. He simply said something vague "I wouldn't hold my breath" Now that might sound like a lie, but it really isn't since there would be no reason for him to hold his breath over it.
Look at it from the standpoint of a developer who doesn't have a character in the game. You are asked, now you could tell the truth, but what would that get you? Maybe a few points with the fans. But why not be a little dodgey and through them for a loop. "No comment" is not a lie, but it does make it sound like you are holding back. This creates buzz, excitement, gets people talking about your game again. Then when it doesn't actually happen, you aren't to blame because it was just the fans getting excited over nothing.
Right now there is nothing a developer can say to fans when asked about Smash (regardless of if their character is in or not) because if they tell the truth that their character isn't in, fans will still argue it is a lie for "NDA reasons" Likewise if they stay vague then they are "clearly unable to say anything because of their NDA"
I think Epic Games is just doing what they can to keep people talking about them, since simply saying "No" wouldn't do them any favors and still wouldn't make their hopeful fans from believing them. Their recent business practices suggest that they are not beyond a little verbal gymnastics if it gets them attention, which to them equals money.