Note: This post contains major spoilers for Avengers: Age of Ultron! Read at your own risk!
Now, with that out of the way, let's continue. So, you all may be wondering, "What could Age of Ultron have revealed, besides Thanos getting the Infinity Gauntlet and revealing that he would get the Infinity Stones himself"? Well, it's also not 'Thanos is gonna kill Vision'. That's old news.
What I am referring to is in the beginning of the film, where Tony Stark/Iron Man has his vision/dream by way of Scarlet Witch's abilities.
Stark's vision sequence
So, in his vision, Tony sees all of the Avengers dead, besides himself, he kneels beside Captain America. At that moment, Captain America grabs Tony's hand and says, "You could have saved us, you could have saved us." So, what the hell does that reveal?
It reveals death, major death!
More specifically, it reveals that Thanos will kill Hulk, Thor, Hawkeye, Black Widow, and Captain America. On another note, I believe that this vision of Stark's is after Thanos is defeated in Infinity War part two, assuming that because no battle sequence is even hinted at in that vision. So, at the end, Stark walks among all the dead, and Captain America utters his last words to Stark. I think this means that afterwards, Tony Stark will fully destroy his Iron Man suits and quit being a hero and just give up. Another thing to note, Captain America's shield is seen broken in the vision.
So, that is my theory on Avengers: Age of Ultron tying in to Avengers: Infinity War. Please comment and tell me if My theory is bull crap, or not. Until next time, Goodbye and thanks for reading!!!