Greg Christie may have played a key role in developing the first iPhone, but he won't be hanging around Apple for much longer. The company has partly confirmed a 9to5 Mac report that the high-profile interface designer is leaving the company later this year after nearly two decades of working at 1 Infinite Loop. Just why he's hanging up his badge isn't certain. The 9to5 story contends that Christie and senior design VP Jony Ive had a "falling out" over iOS 7's design direction, prompting Christie to head for the exit. An Apple spokesperson, however, says that the executive has been "planning to retire" and notes that he "worked closely with Jony for many years." If there are any sour grapes involved, it's not apparent from Cupertino's official position.Regardless of who's right, the departure may have a big impact on Apple's future design strategy. As the VP in charge of the Human Interface team, he has significant sway over the look and feel of both iOS and OS X. His retirement may be a significant loss similar to that of Scott Forstall in 2012. However, it's not necessarily a turn for the worse. If Jony Ive will soon have greater control over interface design, as 9to5 claims, Apple's hardware and software teams may work together more often -- a potentially important move when the company has already said that it's expanding into new product categories.