Joke theory: credits song #6 will be the digirap.
Real theory: Vicious mode are essentially "dark" evolutions, which gives the unnamed form as "Meicoomon Vicious Mode".
Meaning, we may see non-vicious modes, which I think will look less "I want to shred you to pieces" and more "I'm tough, but kind".
Crack Theory: Meiko is secretly behind everything, she just wiped her own memories a la Light Yagami to feign ignorance.
Real Theory: If Yggdrasil and the Royal Knights are the antagonists, maybe the reason they targeted the 02 kids was because they needed Veemon to become Magnamon in order to have a full set of Knights. And maybe Omegamon too.
However, they can't do that for Magnamon, because there is no other veemon in the adventure universe (episode 37 of 02 mentioned that the 02 group consists of literally every digimon the sovereigns could find that was capable of armor evolving)
I just thought they were "extinct" Digimon... and so they had them set aside or whatever. Would be wierd if more were running around, though.
What does extinct mean in terms of Digimon though?
Like what stops a Digimon from evolving into a Vmon at any moment?
The only thing I can think of is maybe the majority of Veemon's data was irrevocably lost at some point. Whatever the reason, it seems to no longer be a problem as Daisuke's child in the epilogue has a DemiVeemon which would likely evolve to become a Veemon...probably, maybe I dunno.
"When the dark digivice appeared in this world, we could only find three digimon capable of using the ancient evolution. But among the children who held the original crests, two of their digimon were able to use it."
Within most of the anime and manga universes, evolution seems a lot more restricted than outside of them. If you take all the extended universe stuff, pretty much any digimon can turn into any other digimon for any reason. However, the series tend to limit itself only to evolutions to somewhat similar creatures, with many digimon designed to be particular evolutions of other digimon (there are some exceptions in the first season due to that adopting the v-pets, however even there you could see they went for the more similar designs. Also, contrast the armor evolutions intended for the show, and the armor evolutions designed for outside the show, and you'll see a massive shift in design paradigm.).Like what stops a Digimon from evolving into a Vmon at any moment?
As such, I don't think there's that many, possibly even any, digimon that could have turned into v-mon