It is obviously no surprise that Disney and Marvel Studios wanted Whedon back, as the first film is third on the all-time worldwide box office list with $1.461 billion.
UPDATE: Marvel Studios released the following statement regarding Joss Whedon:
“Joss Whedon has signed an exclusive deal with Marvel Studios for film and television through the end of June 2015. As part of that deal, Whedon will write and direct Marvel’s The Avengers 2 as well as help develop a new live action series for Marvel Television at ABC. He will also contribute creatively to the next phase of Marvel’s cinematic universe.”
So it definitely sounds like we’ll be getting The Avengers 2 in 2015.