If the Cero-Z rating really does effect Doom Guy's chances then he would have said in an interview "No! Doom Guy cannot be in Super Smash Bros Ultimate!" and until he does, it's fair game.
Ahhhh! Interesting topic you stumbled on!
The interviews... Huh... They indeed said that stuff, but... What constitutes a NDA nowadays?
I don't really know if saying you have had talks with a company is a NEAR breach, or eye-brow riser... Maybe Pete Hines got an earful for that...
Maybe that "Oh yeah" was a bit too much? Anyone at Nintendo would have slammed a desk, wanting an explanation...
But it also could mean there were no plans whatsoever with Nintendo or they refused collab...
I wanna keep hopes, but ignoring these important details is lying to myself. Until they are explained, I will feel at rest.
EDIT:
https://twitter.com/PushDustIn/status/1171719707453349888?s=20
It seems a "column" with Sakurai has been leaked. (It's like a blog). It may say who are the DLC fighters planned or loosely say what it might say, who knows?. If someone can see further, it's welcomed. Everything should be fully leaked in 12.5 hours, as stated here.
EDIT 2:
https://youtu.be/vA7Xyh5YKwA
Apparently, polls were faked. True or nah, I just don't trust leaks, lol. Maybe from actual official sources, sure! (Like SNK leak from Nintendo). So take what I said on my first Edit with skepticism.