If you're like me, when news broke that Iron Man 3 would be based off the Extremis story arc, you expected that Tony would inject himself with extremis, giving him his powers from the comics. In exchange, in Iron Man 3, Tony created tech which gave him an ability simular to the telekinetic powers he gained from extremis in the comics. While Tony didn't gain his powers in Iron Man 3, I'll exlplain why he may in the upcoming Avengers sequel.
He still has a hole in his chest:
To help deal with his PTS, Tony had his arc reactor removed along with the shrapnels in his chest. I'm not a doctor, but I'm postive that you can't just sew the hole he has in his chest up like a normal wond. I take it that Tony put something in place of the arc reactor to fill the hole, but the hole is still there. Like any person, Tony may not want that hole to stay there forever now, especially since he doesn't need it there to survive anymore. Well what better to heal it than extremis itself?
He may need it in battle with Ultron:
Ultron is an Avenger villian for a reason; it takes an alliance of Earth's mightest heroes to defeat him. In hopes of giving himself and the team an edge Tony may look to extremis to give the team a better hand against Ultron.
He may need it to survive:
Tying into the theory above, Tony may not initially think he needs an edge in battle against Ultron. This initial thought may get him extremely wounded and leaving extemis as the only thing that can heal him.
He may need it to deal with his PTS:
Building numerous suits was one of the few ways Tony was able to keep sane in Iron Man 3. With the introduction of superpowered beings and aliens in his life, Tony felt he had to rely on his suits to survive; now with extremis in his world Tony may inject himself to feel less small in a large universe.
Now the question is how does Tony get his hands on extremis? Two theories:
1. He learns the formula after creating the cure for Pepper.
2. If AIM plays a role in Avengers AOU, he may be able to retrieve some from them.
So what do you think? Do you think Tony could gain his extremis powers in Avengers AOU? Do you even want to see a extremis powered Tony? Let me know below!