With the smash success of The Avengers, Marvel has firmly and emphatically created a tentpole franchise meant to unify all of its intellectual property. From now on, Iron Man, Captain America, Thor, The Hulk and other heroes will be working in service of that series.
However, there are some logistical issues complicating that. For instance, Robert Downey Jr.'s Iron Man already had his own franchise going before The Avengers ever came to fruition. While subsequent installments of any Marvel movie need to take this into account, the Iron Man films need to be strong in their own right to maintain the integrity of the character.
Fortunately, it looks as if director Shane Black is going to make sure that happens. Watch the just-released trailer for Iron Man 3 (via HypeBeast) below. Some things to note include Ben Kingsley as villain The Mandarin, Guy Pearce as an unnamed adversary and some reference to New York, which probably refers to the events in The Avengers. It also appears that while Tony Stark had to learn to work in a team the last time around, now he has to understand how to live with himself as Iron Man.