For the sake of saying it, here is my stance with each unconfirmed veteran's chances of returning.
Almost Assured
Ness: O12, a unique moveset (excluding his clone), and since we have Mr.Saturn and the Franklin Badge returning, there is basically no fear for him not returning.
Jigglypuff: O12, a unique moveset with the closest contender being Kirby, who is about as similar as Link to Marth, and can represent fairy-type Pokemon. Next to Sylveon, I'd argue she was the largest face for the type in the community.
Mr. Game & Watch: By far the simplest to design/animate fighter. His attacks have 5 or less frames. Everything about him is unique. No reason to be cut and got that soft confirmation with PacMan's trailer.
Ganondorf: Sakurai's main. The largest, most prominent, and most crucial villain for Zelda as a franchise. Falcondorf (which I hope stays) or not, he is too important for the established series and to Sakurai to dare be cut.
Wario: Nobody can properly dispute that this 400 pound Greed King and his quadruple chin isn't unique or iconic in Smash. With his symbol shown for 2 assist trophies and the E-Shop soft confirmation, it is a matter of when, not if.
Fairly certain
Ice Climbers: Call it Sakurai Bias, but as he chose this pair as the NES emissaries for Melee and how they were cited to be worked on (with some problems) over half a year ago, I feel like they would have been fixed by now. A unique entity as a fighter with their Polar Bear seen, good enough evidence. I still believe all Smash Run enemies are from a series with a playable fighter. All SSE characters technically share the Mii fighters logo.
That's Not Falco: A top-tier clone the fans love who has become a lot more of a semi-clone. I stand that IF Star Fox goes down to 2 reps for some reason, he is staying.
R.O.B.: A unique retro/hardware character whose only reason for being cut, by most people's logic, is because he was unpopular. However, most of that rage was because of people blaming the robo for "taking another character's slot" which isn't true.
Risk Veterans
Lucas: With Mother being dead, and how similar he was to Ness, some fear that Lucas may just be moved into Ness's custom specials. I don't think this will be the case, but Lucas is one of two characters I see returning with a feasible chance of being cut.
Wolf: I am prepared for the hate that will come for saying this, but Wolf arrived on the scene as Star Fox was in its downward dove of popularity and sales of recent games that would only continue (to put into perspective, Fire Emblem: Awakening BARELY sold less than SF643D and Command put together, and the vast majority of Star Fox fans are in North America) as a quasi-clone of almost Luigi tier. The problem is, his differentiation lead to him being less viable and loved than his rivals. I don't believe Wolf will be cut due to being the quasi-clone he is and Sakurai wanting him in Melee, but ii wouldn't exactly be surprised.
Unique Cuts
Mewtwo: Dead. An impressive character but an abysmal fighter. He would require the work of a newcomer to return and even as a Pokémon fan I don't want him back when Lucario functions as a spiritual successor that plays well.
Squirtle: My favorite starter in Kanto, but with Charizard solo and Greninja as a speedy water starter, I don't think he has a place anymore.
Ivysaur: Same relative boat as Squirtle, but lacking someone to take his place as a surprisingly heavy grass starter unless Sceptile takes his place. And I feel Ivy had the most iffy moveset of the trio.
Snake: With 3 third party characters here, Sonic revealed so early, and NO sign of Snake when these other 3 have been so played up, I don't see him returning. Personally I have a bit of joy because I never connected to him and had some annoying campers with his arsenal that leave me with no fond memories.
Never Coming Back
Dr. Mario: The first thing that came to mind for Smash players when alternate costumes were announced. The poster child of the idea. No major differences to warrant the thought of being playable.
Young Link: Toon Link does all that YL tried to. All that is missing is that 7 second taunt.
Roy: Arguably the worst Lord in Fire Emblem history, his fire gimmick now belongs to Ike, and Lucina as a Marth clone with a better trade off for Marth's tipper and exchanged power for speed and air control. He has little value to his home series and less in Smash now.
Pichu: The fact that it is cute is the one and only redeeming factor. I loved using her, but she was objectively the worst character and served no real purpose.
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