Debney himself confirms that he's going to score
Iron Man 2 (or is close to getting the deal) in an audio interview posted on Filmmusicsite.com today,
check out the link here. Click play and fast-forward to 32:22, that's when Debney talks about it.
He says he'll probably compose the score from scratch, but is quick to say that he liked Djawadi's score in the first film.