Considering that Nintendo has the ballot data and made Smash decisions based on that data, I would be surprised if they don't add them in.
If you look at it from a business perspective, there are more Smash playing Switch owners hoping for Banjo-kazooie. Nintendo has shown that they keep their ears to the ground about what fans want. K.Rool, Ridley and Simon is proof of this. I wont doubt Minecraft's popularity and sales, but from a smash perspective, Banjo-kazooie would be more profitable. I know for a fact I will buy the whole pass and the inevitable Banjo-kazooie Amiibo. I doubt people are going to shell out for a Switch, Smash and DLC because of Steve.
Well said, Banjo-Kazooie caters and appeals to Nintendo's audience especially the older ones who have been playing Super Smash Bros since the N64 era (1999) and Melee during early Gamecube (2001) which was also when the Banjo-Kazooie (1998) franchise was in it's prime
Hardcore Smashers will likely shell out the cash for DLC fighters especially fan requested ones more likely than casuals who will likely be happy with just the base game or would be unaware of it especially kids.
Also keep note that while MC is popular, The Switch install base isn't as big as other consoles even PC or Mobile, People who play MC on other devices other than Switch probably don't even give a damn about Nintendo let alone Smash so even if MC gets DLC, I don't think people are gonna buy a Switch, Super Smash Bros Ultimate, Extra Controllers, Online Subscription to play a $5 DLC guest character,
You know who gives a damn about Banjo-Kazooie? Nintendo fans and guess what ? They already own Switches and copies of Super Smash Bros Ultimate that are more than happy to pay an extra $5 to see the bear and bird return.
A big portion of the Super Smash Bros fanbase are hardcore Nintendo fans that play and care about most of Nintendo's 1st Party franchises which Banjo-Kazooie were pretty much a part of during the N64 era marketed along side Nintendo icons such as Mario, Donkey Kong and Pikachu, That's why there is such heavy demand for the them and you can see it in voting polls and most Youtube videos Top 5 or 10 list.
We can also all agree that if it wasn't for the "Buyout" They very likely would have already been on the roster by now.