Remember that Ive wanted to move back to England a couple of years back, and Jobs had to convince him to stay.
Since that point he's proven himself on just about everything Apple has done, save some lack of execution on iOS 7. Maybe he's just really ready to move on, and try either design on other subject matter, or try challenges outside of design.
Or maybe he once again wants to get the heck out of California. In particular, our taxation system dissuades high performers to stick around, and maybe he doesn't buy into the values of this place, either. (Speaking as a disgruntled Californian.)
Since that point he's proven himself on just about everything Apple has done, save some lack of execution on iOS 7. Maybe he's just really ready to move on, and try either design on other subject matter, or try challenges outside of design.
Or maybe he once again wants to get the heck out of California. In particular, our taxation system dissuades high performers to stick around, and maybe he doesn't buy into the values of this place, either. (Speaking as a disgruntled Californian.)