The headlines related to Mark Papermaster leaving Apple seem heavily weighted toward connecting the dots between the iPhone 4 antenna "death grip" and his leaving. The Wall Street Journal says Apple Executive Exits After iPhone "Antennagate", the New York Times declares Executive Leaves After iPhone Trouble, and The Register bluntly states Apple Hardware Exec Falls on Sword.
The reason that it is unlikely that Papermaster's departure is antenna fiasco is that Apple has never admitted it's a problem. In order to have a sacrificial lamb take the fall for a corporate debacle there must first be a mea culpa where the corporation admits that there is a debacle.
Apple has that there is nothing wrong with the iPhone 4. The company told users they are holding the phone wrong. They directed whiny users to get a case to impede antenna interference if they really think it's that big a deal. Only after much media attention and user backlash did Apple finally agree to address the issue at all.
While the fact that Apple announced a plan to experiencing a problem might seem like an admission of guilt, Steve Jobs spent 75 percent of the press conference demonstrating that every smartphone has an antenna death grip issue, and extolling the virtues of the iPhone 4 as an engineering marvel. He even went so far as to claim--with a straight face--that Apple intentionally put the little line in the antenna at the bottom left corner of the iPhone 4 specifically to mark the position that users should not touch.
What Jobs did not do, and what Apple has yet to do, is to actually state that the , or apologize to iPhone 4 users for the design faux pas. If we accept the position of Jobs and Apple on the antenna issue, then it makes absolutely no sense for Papermaster to suddenly resign to take the fall.