That's probably fine for both parties, since its not entirely clear how well Iguodala will fit if/when Young emerges. A shorter deal probably makes him easier to move if things don't work out.
If I were Iguodala I'd be a little worried that he might be more of a Magette type player in 4 years, since he will no longer be young, and likely won't be a top 2 scorer on the Sixers. He could very easliy be forced into a MLE type deal like Magette alsmost had to take if things don't fall his way.