Avengers: Age of Ultron is about two months away from being released, and Marvel hasn't revealed much about the plot. The latest trailer showed a little more of the plot, but this movie is going to be really long, and many parts are still being kept in the dark. So, what do I think is going to happen? Buckle up and hold on to something, because I'm about to get extremely theoretical and unnecessarily vague.
1. There will be an Infinity Stone.
Okay, we already know that Loki's Staff is in the movie. And, thanks to Marvel's big press conference that revealed the entire phase three lineup, we know that this Staff is definitely an Infinity Stone. Still, I believe that to establish an interconnected world of Infinity Stones, Marvel needs to focus on a different one in every film. And since time travel is used in the comic book arc for Age of Ultron, I wouldn't be surprised if the time stone was used to get the Avengers out of this big mess. Plus, we saw that part in the trailer where Captain America's shield was destroyed, which foreshadows death, which foreshadows time travel to save the team. I know it's a long shot, but I seriously believe that this is a major possibility (even though the death scene may be just a vision provided by the Scarlet Witch) (Vision pun intended).
I mean, it could be that they spotlight Loki's Staff in this movie since they were focused on the Tessaract in the last one, and maybe they'll introduce another stone that will play a bigger part in a future movie before Infinity War. In addition, Josh Brolin has been added on the cast list for Age of Ultron on Google (but not on IMDb), so he may play a bigger part than previously believed (or he may just be in yet another post-credit scene).
2. Hulk is leaving, trust me.
The Hulk is definitely leaving by the end of the movie. I have no doubt about this. I don't care if he gets sent off to space, goes into hiding, or dies. There is absolutely no way that he's still going to be around while Civil War is happening, because a) if he's there, he ruins the whole story line, and b) there's no reason for him not to show up unless he leaves.
I know that Kevin Feige (or whoever did that interview) has all but confirmed that the Hulk won't be going into space, but he's obviously going to turn on the Avengers, and I don't think he'll stick around after that. Don't get me wrong, I love the Hulk as much as the next guy, but I seriously doubt he'll be around for Civil War. I do, however, think he'll be back for Infinity War (because the team will beg him for help).
3. The team will be disbanded (or something like that).
The repercussions of Avengers: Age of Ultron will be massive, especially if the Hulk leaves. Pretty much everyone has guessed this so far, but I think that the Avengers will disband (or a few will quit) in the wake of the events that have shaken the world. Thor will go back to Asgard in fear of what will happen next (Ragnarok), and Tony Stark will most likely quit because he believes he's hurting more than he's helping. As I've pointed out earlier, the Hulk will almost definitely leave, and the only people left are Captain America, Clintasha, and the Maximoff twins.
I'm not sure what will happen to the twins. I think they might stand and join the fight for justice, but they also might just want to go back home and help rebuild it. I think Clint and Natasha will stay (since they're already confirmed for Civil War) unless Black Widow decides to take some time off in light of Hulk's departure.
Altogether, this movie will lead into a fantastic phase three that will lead up to the great and mighty Infinity War that will rock across the MCU and basically have everybody. Despite all of my theories, I hope the movie turns out well and if it doesn't, I probably won't be able to tell anyways.
(P.S. You probably noticed that I didn't write anything about the Vision besides that terrible pun, and that's because he's an absolute wildcard to me. I'm not even sure who's building him yet!)