Ganon
I think this is one of the more realistic options for a Zelda newcomer and there aren't that many. Tingle has his merits and deserves to be playable. Impa is another option, but obviously the clock will need to be turned back a few decades (a Sheik alt is plausible and would be a great compromise; this would be a cool and contextually appropriate nod to the guardian-mentor relationship Impa had with the princess in OoT). Outside of these three, I don't see it happening for a Zelda newcomer. I mean, I suppose Link could practically be one depending on how much of his moveset changes. If he get runes and champion powers, that's a completely different character. The rest? One shot assistants, one shot villains and revisions of Zelda that haven't been in a main game in some time. When it comes to the Zelda series, Sakurai hasn't shown a willingness to invest in characters with limited appearances. Sheik remains soley because she's been grandfathered in as a veteran and was Zelda's alter ego anyway.
Moving on, Ganon has a fantastic legacy and offers an array of interesting possibilities: dual great sword-wielding melee terror, trident-wielding pyromancer (my personal favorite depiction) or heavyweight sorcerer. Each of these is a niche that's not been explored before and would be worthwhile concepts to bring into Smash. So he's got that on his side. Secondly, the guy is super duper important in every game he appears in. He's either a standalone entity or Ganondorf's transformation. Often times, he has the illustrious distinction of being the game's final boss. In all cases, he's part of the triforce three, which is a theme Sakurai has demonstrated that he's comfortable revisiting more than once, whether we've been excited about that idea or not. Lastly, Ganon bridges generations. He was there in the beginning and he's here with us now in 2018. Every Zelda fan knows who he is and every Zelda fan has their connection with the character. That's big and this is important to Sakurai. Ganon not only has a future, but he has a long and storied past.
Chance: 20%
Want: 100%