Anyways, I think Banjo and Kazooie are actually not unlikely. I believe the DLC folks will be big names, or at least figures from popular games. Maybe Joker is the "least known" in terms of popularity of all DLC fighters. I mean, Persona has grown in popularity in the current decade (almost no one in the west knew about Persona back in 2009 when I played Persona 4 on the PS2), Anyways, my point is that since DLCs are paid, it makes more sense to release names that will likely bring a good profit rather than niche fighters, with questionable popularity.
Now, Banjo-Kazooie hasn't been relevant in several years, however they are still big names and still very popular. Of course, if we are talking popularity, the Minecraft guy is obviously more popular these days, but he doesn't have a history of Nintendo like Banjo and Kazooie have. Granted, if we talk about history with Nintendo, a Persona fighter wouldn't be a thing (we would possibly have a Shin Megami Tensei fighter instead, perhaps Flynn or Nanashi from the SMT4 games, who knows - Or Hitoshura/Demifiend, even if his game is on the PS2). But there is a theory that Joker was chosen because among other reasons, Persona 5 is coming for the Switch. I try to not put too much thought into that so I don't raise my hopes up for Solaire (since we randomly got Dark Souls in the Switch this year, something I would have never expected).
My main point really is that I believe Nintendo and Sakurai would want to make sure the DLC would sell and for that reason, picking "characters" that are likely to make people talk as well as make them interested in spending $5 on the fighter/stage/music pack is a must. Which is why as much as I want someone like Dixie Kong, I am not expecting her as a DLC at all. However, I will not be surprised if Banjo and Kazooie show up, and I will be thrilled if they do.