I think people really need to really think about what we learned through that presentation after rewatching it, and everything we know, and they should stop taking everything as "It's black or white" face value. So far, what we can take from what we learned...
"THE PROTAGONIST RULES IS GONE!"
It is not. The protagonist rule is still in place, and visibly, it even was Sakurai's concern as he did bring up "Wait, why no SpringMan" when talking with the ARMS director, he claimed that "All characters are Protagonists" which, whenever you hate it, like it, or try to find a spin on it. In the end, the Director/Creator have the last word, and we must go with their words.
"SPIRIT RULES IS ****ING GONE! WHOOOHOOO!"
I think that one is more nuanced than that. And people really should calm their horses, and not see it as "IT DECONFIRM" or "THE RULE IS DEAD". As in like, each characters has it's own context behind it and should be taken as it's own case.
It's also important to remember that visibly, ARMS is a special case, EVEN in the Smash development itself, as it was a request from Nintendo, and from the way Sakurai talk about it, it seems that Nintendo rather told him to make a Fighter from ARMS instead of a specifics characters, and he then went to look out for a character, visibly himself going for Ninjara, before asking what the ARMS creator would want in smash, where he clearly asked for Min-Min.
Try to be a japanese game developper refusing your co-worker's wish and character from his own game because you made it a Spirit.
That...Wouldn't fly, even by Sakurai logic or whatever fan-rules that exist. As such, Min-Min being an Upgrade is great in that sense, but should be taken so far, as a first case scenario, opening possibilities, instead of a "Yeah, it's totally happening."
There is also the special case of Spirit Events, which In my opinion still hard deconfirm any characters appearing there. Even more Third Parties event ones. As those spirits and event would just be overlapping with the current DLC schedules if they had a DLC characters that was going to happens, by that I mean-
Why would you make a Resident Evil Spirit Event, if down the line, especially with the timeline they released, you made a deal for a fighter AND Spirits that would be sold togethers nonetheless?
Basically, for Spirits, it should be taken as a "Hey, it's possible, but she might be the only instance of it because of the context" than "OH **** YEAH LET'S GO! ZACIAN NEXT FIGHTER ON MY WAY!" for exemple with Pokémon.
"AT ARE NOT DEAD!"
I think the fact that Sakurai was thinking about Ninjara himself and not Spring-Man sneakily tell us that he consider Boingy Boy represented enough and that he wouldn't Upgrade and AT.
"WHAT ABOUT MII COSTUMES?!"
DLC Mii costumes are still for me the hardest deconfirm you can get for a characters, and even probably a company. For exemple, Heihachi being deconfirmed today, totally rule him out for the Fighter Pass 2, however, it doesn't rule out Namco, who could get a Tales of Characters for exemple, with Mii Costume focused on RPG/Tales of. But not only that, Heihachi's Mii costume being back, also put the remaining 3rd Parties Mii Costumes and Characters that have yet to come back from S4 in a very shaky spots.... (Hi Lloyd and Geno.) where them coming back in a future pass would also decomfirm them.
HOWEVER- The Vault Boy Mii Costume is a special case, where I'm willing to take that extra-step and say that Bethesda won't get any character this pass. Why?
I think that, in the event where a company would be introduced in Smash, they would bring their set of Mii Costume with them, like we saw with Cloud, Joker, Hero and Terry. Banjo being the only surprising omission probably because of Microsoft.
I feel that it would be weird to release a Fallout Mii Costume, when you could release it alongside let's say DoomGuy in a Mii Costume showcase focused on their IP, just like the others did?
That's all, that's the most rational way to look at the situation, where nothing is a guaranteed until proved otherwise, some "rules" still stands, others do not, unless we see down the line that it was just a special occasion exemple, if we see that Min-Min was the only promotion of this pass.
I'm now excited to see where the speculation will go. But I just hope it won't go too crazy and toxic, and people will stay with the famous "Hype responsibly" and "Think before Hyping."