With the director's chair on Iron Man 3 now opened after Jon Favreau decided he didn't want to return, attention has quickly turned to new possible helmers.
First up and one that may make the most sense given that he helmed Robert Downey Jr's comeback flick, Kiss Kiss Bang Bang is Shane Black. He also has a background scripting action with genre classics Lethal Weapon and The Last Boy Scout to his name, and would be a brilliant choice; but he's tenuously committed to Manga adaptation, Death Note. May be an issue that he's never directed on that scale before which could be a stumbling block if Marvel are looking for a steady hand with the budget etc. Next is Slither writer/director James Gunn, whose small budgeted vigilante flick, Super, is currently garnering mammoth buzz. Gunn is apparently meeting with studios about big directing gigs and would be another brilliant choice to continue the franchise. But he is an edgy, sardonic writer and director who again has little experience handling huge budgets.
Marvel are not adverse to taking risks with tent pole franchises and if they did, those two men would be my top choices. Hardly means it's going to happen, but I wouldn't write either off given their talent and previous work.