Frenchie fibber/director Louis Leterrier supposedly spilled the beans straight out of a Marvel meeting with Jon Favreau, but don't get too excited. He's been known to play fast and easy with the facts...
This from Den of Geek...
Louis Leterrier says new Avenger will feature in Iron Man 2 and Jackson, Downey and Norton set for Avengers in 2011
Louis Leterrier has revealed not only that Jon Favreau is currently writing Iron Man 2 with Robert Downey Jr., but that the sequel to the Spring blockbuster will feature a new character from the Avengers, after the brief appearance by Samuel L. Jackson as Nick Fury in the post-credits sequence of Iron Man.
Additionally Leterrier is reported to have said that 2011 will definitely bring Jackson, Downey Jr., Hulk actor Ed Norton and two other 'A-list actors' - presumably whichever A-listers get cast as Thor and Captain America in their respective upcoming movies that Marvel is also producing - together for the Avengers movie.
All of this news is brought to us via a DoG scooper who supposedly spoke with Leterrier right out of a meeting with Iron Man director Jon Favreau at the Marvel Night at the Grand Rex in Paris in early July.