Like I said in the original thread, I was one of the fans who got into Digimon Adventure back when it was on FOX Kids in 1999. I didn't know it as Digimon Adventure back then, but by its improper localised name "Digimon: Digital Monsters" complete with changed names, censorship of numerous things, and of course all those DC/Marvel style corny jokes through the whole thing; no matter if they were battling or not. Watched "season 3" but it was really its own series. Today, I understand that the series turned into a rebooting type of series every season or so, but back then I was disappointed season 3 had nothing to do with the first two. But I liked it well enough. It was good by itself, but just not good when I held it up to the first two seasons. Then I learnt about "season 4", which is Frontier, and I officially stopped watching it due to how lame I felt it had become. I went online seeking to watch Digimon Adventure as a result and found the original Japanese version of it and discovered how good it was and just how sh*t the Engrish dub is. Haven't gone back since. I've watched Tamers in the original Japanese, and I still like it but still not as much as Adventure. Watched the first episode of every season following Tamers, but the concepts are all sh*t. But then, on Aug 1 2014, they announced Digimon Adventure Tri, and I actually became excited for new Digimon for the first time since 2001. Its like being a kid all over again when a new movie comes out.

Maki seems to know more about what happened to the 02 chosen children than she's telling everyone, including Daigo. We already know she's been working with (for) Yggdrasil but only to make the reboot happen so she could see her digimon partner who was sacrificed during the fight of the original five chosen children vs the dark masters. They don't tell us when the original five were in the Digital World but I have a hunch its 1995.
Personally, I think Yggdrasil created the new infection and that Maki provided Meicoomon to be the specimen. After all, its obvious she has a history with Meiko. I think Meiko's digivice may be Maki's, and she gave it to her as well as Meicoomon. The reason being is the symbol that appears on her digivice when Meicoomon's infection flares up (which happens when she gets upset) also appears on Maki's digivice in the flashback after her digimon partner was sacrificed. I also do think that Gennai is the same Gennai, but reprogrammed by Yggdrasil so he has more help.

Basically, Yggdrasil wants to destroy the real world, which implies the Digital World can exist independently of the real world. And the Meicoomon's powers are how he's going to carry that out. But without being able to control her I think he created a virus that could inhibit her reservations and maybe even her free will. And given that Gennai gave that agency (White Fang?) all the information about digimon, I'd say this agency is fairly new and Maki & Daigo work for them because of the fact they were chosen children. So I'd say at most the agency is only about two years old.
Homeostasis wants the two worlds to coexist in harmony. We see the realisation of this in the epilogue of Digimon Adventure 02 where everyone in the world had a digimon partner and could freely enter the digital world whether adults or children, where during Digimon Adventure season 1 & 02 adults were considered corrupt and not accepted in the digital world, though they could still physically enter ie Oikawa. I think this is part why Yggdrasil is only now going rogue on the real world, because the chosen children are all too old and still have relationships with digimon. Of course, even then, it would be only a small part of his motivation to destroy the real world.

The goggles are Taichi's, by the way. The official Twitter already confirmed it. This coincides with the fact Hikari says "Big brother, why?" when they show the goggles in the trailer. This implies he did something reckless (again). This has spawned a couple of different theories as to what happens probably toward the middle of the movie (We see them back in the real world in the trailer so the battles likely happened before they returned.)

1) During the battle between Meicrackmon/Alphamon/Jesmon/Omegamon, I think Taichi jumps in front of an attack to save [somebody] and that makes Hikari upset, therefore susceptible to whatever it is that ends up possessing/infecting her. The text on her face is overlapping too much for me to be able to make anything out. But if anybody is able to get even a little bit of it cudos to you! ANYWAY, this causes Tailmon/Angewomon to evolve to Ophanimon Falldown Mode and she attacks Meiko (we see Ophanimon Falldown Mode then they show attacks raining down near Meiko) and probably Meicrackmon as well. I think the fight will end soon after that, probably due to Meicrackmon slipping through another distortion to the real world, and Ophanimon Falldown Mode reverts to Nyaromon thus we see the scene where they show HIkari with the purple text all over her face and a voice calling to Hikari.

2) Something happens to cause Hikari to fall susceptible to infection/possession during the battle between Meicrackmon/Alphamon/Jesmon/Omegamon causing Tailmon/Angewoman to evolve to Ophanimon Falldown Mode and she attacks Meiko and probably Meicrackmon as well. Then I think Taichi will step in front Ophanimon's attacks on Meiko (We see in the first trailer Taichi running toward Meiko & Yamato and it appears he is about to be blown back right before it cuts away) snapping Ophanimon out of Fallout Mode and she reverts to Nyaromon and she starts calling to Hikari and snaps her out of her mode thus we see the scene where they show his goggles and she says "Big brother, why?"

Haven't made up my mind which one is the closest to what will happen. They both seem equally plausible.

The thing I wanna see is what's going on with Maki. She didn't react too swimmingly when her digimon partner didn't recognise her due to the reboot. I can't wait to see what she does next and how Daigo will be involved in it. The whole thing with Yggdrasil and Meicoomon won't conclude til the 6th movie. So I'll hold my thoughts on that til I see Kyousei.