What if Menoa is Kōshirō's mysterious American friend who has been mentioned since
Our War Game!, then once in
02 (which the dub replaced with Wallace), and all the way up to
tri. but never seen or actually even
named? Since this is supposedly the end of the
Adventure universe's story, perhaps they decided to
finally show that enigmatic person.

Originally Posted by
Vaioumon
Random theory: "Last Evolution" is literal. The "phenomenon" is the partner digimon are becoming so adapted to the real world that they're becoming less "digital" and more "real", to the point where they'll soon lose the ability to change form and will start aging. The children will have to decide if it's worth taking that away from them to stay together. This pisses off Yggdrasil (if not!Gennai is to be believed), who sends whatever super digimon to shut them down, leading to the chosen children's final battle "for real".
I don't think Yggdrasil is still a thing. Homeostasis shut it down at the end of
tri., remember?
And your idea for "Last Evolution" is interesting, but I still think it's probably a new kind of Evolution, perhaps a fusion between humans and Digimon, like it was suggested by someone when the first trailer came out.
Unless that idea has already been shot down in an interview. Has it? I have been too busy to pay attention to
Digimon news recently.