Man, I remember my old buddy here, lokidionysus who used to claim to have worked on a focus group, and had a lot of speculative info.
He was run off the board, and I used to communicate with him over email and pick his brain a bit. A lot of his speculation was off, and it differed but there were a few plot points that stayed consistent.
The things he told me between 2012-2014
Nebula and Ronan in GotG WAY before they were announced
Ultron is going to be the Villain in A2, or A3 and that part of his story is involved in an alternate future where he wins, and Scarlet Witch was connected to that (BEFORE Scarlet witch was announced for these movies...and we saw her vision)
He also said Ultron is at war in the future and is trying to change the past in AoU to win a war against Kang/Immortus, in order to stop Thanos ("and believe me, he's winding up" "I was a dream, but now I am awake").
He also was insisting that Fiege is going to get the rights back to the Fox characters, told me this in 2013. He was also insistent on Thanos using one of the gems to create a pocket universe, that there are two sets of infinity gems (which apparently is the case now) due to Thanos creating a pocket duplicate universe to accumulate all the gems, and then bringing that pocket universe into the main timeline. He also was adament about Immortus having a role in the end of this saga, and Kang being relevant when we get into the light and dark timelines of the MCU. A lot of this stuff that is tough to grasp, and probably isn't true.
But the things he told me back in 2012-2013 before any announcement that turned out to be true
Ronan and Nebula in gotg
Scarlet Witch having insight Ultron's story, before either character was announced to the MCU
MCU getting the rights back from Fox for those characters
Two Infinity Gauntlets
Surtur getting power from a star (we saw that muspelheim is a dyson sphere powered by a star)
possible two timelines in the MCU
Ant-man touching onto the more subatomic aspects of the MCU far before anything about ant-man came about
Stark's role in Ultron
things that havent come true yet
Ultron was a tech, world protective protocol created by Pym but failed. Stark completed it... OR Ultron from the future sent his AI back into another timeline (because he somehow has the time gem) and influences certain events in IM3 that allowed Stark to create Ultron so he can inevitably take over the earth, have the mind stone, and the time stone
Ultron's future war with Immortus/Kang for Time
Thanos' created universe
and The Infinity War story is literally a climatic story between Thanos, Immortus and Ultron.
That probably isn't true, but I think he knew SOME stuff