It seems that the veteran actor of stage and screen, Gerard Sanders, will be playing Tony Stark's father in Jon Favreau's Iron Man. Comics2Film found this news in the program for A Night of Vignettes directed by Sal Landi which is now running in London.
Within the program, Sanders' description reads:
CLICK HERE to see the program.
Iron Man, starring Robert Downey Jr., Terrence Howard, Jeff Bridges and Gwynth Paltrow flies into theatres on May 2, 2008.