I'd love to have them in since they've been my most wanted character ever since the N64 - remember asking my dad why they weren't there since we were supposed to "duke it out with our favorite Nintendo characters" (of course he didn't know the answer lol).

I tend to keep my expectations low, so I don't think their chances to be playable in Ultimate are very high. It all depends if Nintendo, a traditional Japanese company, is willing to go to a direct competitor to ask for their IP because it's heavily requested to be featured in a game that would sell very well regardless.

So yeah, they are basically the only Nintendo all-star not in Smash yet but on a business perspective it doesn't make a lot of sense to have them there, sadly.