Okay so what I'm about to say is super negative as it basically soft deconfirms not only Shantae, but almost all the "most popular as far as we know" character choices... but I want to just get it out there.
Basically, I'm doing a full circle all the way back to the stages thing from the Smash Direct. So before I didn't hold much stock in the no more stages theory, but now we have two brand new fighters and still no new stage.
I'm basically reviving the concept that after Sakurai went out of his way to give such detailed statistics on the stages back when Dracula's Castle was revealed, that we are not getting any new ones before DLC.
I do realize there is no way Isaac or any 3rd Party could possibly get in without a stage, so if that turned out to be right, they would basically all be deconfirmed.
At BEST Geno could MAYBE get away with not having a stage.
Edit: I love that this post went up like right at the same time Shadowknight1 made their overthinking post lol
We have at least one more Smash direct coming guaranteed and the only new ground they would have to cover is the story mode, newcomers and stages. Give Sakurai a chance to surprise you, as he often tends to do.
Besides by 2 new characters I'm assuming you mean K. Rool and Isabelle? 'cause you could make the argument they didn't need a new stage because their franchises are already well represented. Ridley didn't get a new stage either.
You're worrying a tad much
UUUUUGH MACBETH. I *hated* that stage as a kid, especially trying to get to the Venom hard route from it. Stupid train switches... xD
Even if there are more than 2 fighters there's no way Shantae's getting through Incineroar, Ken, Geno, Skull Kid, Steve, Shadow, Isaac, Dante (please no) AND Banjo. Considering that, along with the stage theory and the fact that all of the evidence we have thus far could just point to her being an Assist Trophy, I think i'm jumping ship.
People have already dissected your posts but, yeah no.
Incineroar, Ken, and Shadow are the only ones from there I'll argue is likely. I'm fairly certain there will be a pokemon rep 'cause there's always been one each game.
Ken and Shadow, sure I could see them being echos.
Skull Kid is iffy, but I'm honestly on the side he'll be a boss. If I'm wrong and he's playable, at least I'll get to see LeakyPandy get cancelled because they are 100% adamant on their source(s) saying so to the point they are willing to risk being labeled as un-credible forever.
Dante and Steve are not happening. The former has been shot down repeatedly and the latter just doesn't make sense. Yes I know Sakurai and his team can be very creative, after all they gave Duck Hunt, Wii Fit, R.O.B. and Mr Game and Watch movesets but...just no.
The rest are as up in the air as Shantae only they don't have their companies being NDA levels of silent in regards to the subject.
But you seem to have made up your mind so I won't stop you from leaving. Hope you find a more positive state of mind.