I thought up what would happen in the Avengers 2. Let me put you in on the previous 1st. Tony Stark/Iron Man killed Obadias Stane/Iron Monger in his 1st movie, Bruce Banner/the Hulk bruttaly defeated Emil Blonski/the Abomination, Tony Stark and Lt. Colonel James "Rhodey" Rhodes/War Machine killed Ivan Vanko/Whiplash in the 2nd Iron Man Movie, Bucky Barnes was thought to be lost in the train battle in Captain America: The worlds 1st Avenger, Johann Schmidt/the Red Skull was absorbed by the cosmic cube, and Loki will probably be banished to the realm of silence.
Now for What would happen: Tony, Fury, Natallie Rushman, and Clint Barton explain the Avengers initiative to Rhodes, Loki returns from the realm of silence and revives Stane and Vanko and recovers Abomination and Red Skull, Thor saves Bucky who mysteriously appears falling from the sky above modern New York, Rhodes explains to Bucky about the Avengers initiative, the Masters of Evil are born (Red Skull, unconfirmed Captain America 2 villain, Ironmonger, Whiplash, unconfirmed Iron Man 3 villain, the Abomination, the Leader, Loki, Frigga), Bucky & Rhodes help the Avengers defeat the Masters of Evil, and Bucky and Rhodes are initiated.