Latino Review are report­ing that Tim Rob­bins is set to play Howard Stark whilst char­ac­ters Hawk­eye and Black Widow are rumored to make an appear­ance in the Iron Man sequel:

From what I’m told, Tim Rob­bins is going to be play­ing Howard Stark in an impor­tant flash­back sequence that is going to set up the Avengers and Cap­tain Amer­ica films. Jon [Favreau] wanted to get a good actor because he didn’t think the guy who played Howard in the last film could carry such an impor­tant scene.

The scooper goes on,

I’m also told that HAWKEYE and BLACK WIDOW are def­i­nitely in Iron Man 2 and they wont be cameos either.