I think the potential Zelda newcomer is one of the most difficult things to predict about the new Smash Bros. Since The Legend of Zelda is one of Nintendo's biggest franchises, I think it's likely that we'll get another Zelda newcomer this time around, but who?!
Ideally, I'd expect Tingle, since he's one of the most recurring Zelda characters and the only Zelda character to have his own spin-off games. Honestly, when it comes to importance to the Zelda franchise, Tingle deserves the spot above all other Zelda characters, in my opinion. Unfortunately, with Villager taking a Balloon Fight inspired move that could have easily been Tingle's (and would have made more sense), I don't think he's very likely.
Other than Tingle, I struggle to find any Zelda characters that are worthy of being a new playable character in Smash Bros. There's Ghirahim, who I believe has a ton of potential and is bursting with character, but he's just a one-off villain, and not even the main villain of his game at that. But, hey, he wouldn't be the first one-off character to become a playable character in Smash Bros.
And then there's Impa, whom I already gave my thoughts on. I'd only really expect her if she was added to replace Sheik, but she is one of the more recurring Zelda characters.
Regarding Toon Zelda/Tetra (lol, Toon Sheik), I love The Wind Waker and I love Tetra's character, so it would be great to see, but I don't really expect it. Yeah, she was supposedly planned for Brawl, but I don't think that means we should necessarily expect her this time around. Times change, and she wasn't given priority in Brawl for a reason. I wouldn't expect most of the Forbidden 7 to get a second chance in the new Smash Bros. Out of all of them, I only really expect Mewtwo to show up this time. I believe Roy and Dr. Mario were wise cuts and should stay such after missing out on Brawl, and I don't anticipate Plusle & Minun joining the cast anytime soon. Dixie Kong I could see happening, but she wouldn't be the Diddy/Dixie tag team that Sakurai was planning for Brawl originally.
Also, if Toon Zelda/Tetra made it in, it would feel incomplete without Toon Ganondorf as well, and I don't think that's going to happen.