Joss Whedon has said on multiple occasions that he wants more women in Marvel Studios movies - in fact, he almost had Wasp in Avengers - almost as in, she was even included in the early animatics.
Animatics are animated story boards that help a director and cinematographer better envision how a scene will play out. These leaked ones for Avengers, credited to Federico D'Alessandro, show off some early versions of familiar scenes - the opening of the portal, Iron Man confronting Loki, as well as some that were completely scrapped.
The aforementioned two that show earlier versions of existing scenes are the most interesting though. One, when the portal opens, had the team assemble much faster (Hulk takes out the very first of the giant snake monster things), but that's the least exciting part of it. In an early shot of the team, Wasp can clearly be seen floating in the background. When the aliens start pouring through, Loki is surprised - apparently a different angle was originally going to be played there. Indeed, that's not all for the aliens - their distinctly bumpy-chinned look seems to confrim old rumors that originally we were going to see straight-up Skrulls in this movie, not the Ultimate-named Chitauri that wound up being a different race of aliens altogether.
And then there's that "Tony suitup" scene, where he gets his new armor and chats with Loki. Before Loki hits the scene, JARVIS is talking to Tony. His A.I. sounds downright prideful, telling him he's better than the other Avengers, and that he's built all of this alone. While it's likely some manipulation of Loki's, this does play nicely into our speculation that JARVIS and some Iron Man armor will be what Ultron comes out of for the sequel - could Whedon have originally planned to plant those seeds this early on?
Check out two more below, both featuring alternate ways for Iron Man to come into the movie - including in the very first scene. And head over to YouTube for more animatics, including some from Iron Man 3.