Why I may have only appeared here till now, I have been a closet supporter for this old beer and bird duo so add me onto that list.
Though I will also say if I recall they said they'll be revealing the DLC fighters over time and not all at once, regardless the fighter pass doesn't become available to purchase for anyone outside getting the digital bundle till launch day so there's that as well, so... I think it'd be highly likely for some at least a single piece of smash DLC to be revealed. As they did with the last one they announced Bayonetta 1+2, and 3 alongside the final piece of BOTW DLC, so I don't see why they can't do a similar thing of the Metroid Prime Trilogy, and 4 alongside a DLC fighter, specifically Banjo and Kazooie.
Why them specifically? Well... obviously third party DLC fighters would have been in development first due to the liscening stuff and what not so whoever the Square rep (going with the Vergebend stuff with that) and Banjo would be released and shown off first. Alongside the fact there is data for two rare ips in the games as spirits and Vergebend and other leakers saying Enderdragon will be day one patch content Banjo makes sense and after all the date on the eshop for s single fighter is after the date Piranha Plant's deadline to be released st the latest so at least one more fighter should be releasing then. Plus as I said again, I don't think if the Enderdragon data gets found in a day one patch they'll change anyones classic mode, so naturally... Banjo being a Microsoft/Rare rep would make some sense to fight against it.
Though... this video probably explains stuff better than I could, so watch at your own risk for potential leaks, especially since there's also some non-smash but still Banjo related content in it.