Scott Forstall, one of the most visible faces of Apple in the wake of Steve Jobs' death, is leaving the company in a surprise shakeup at the head of Apple' ranks, according to CNN.

Forstall, a senior vice president in charge of Apple's mobile operating system, iOS, will act as an adviser to CEO Tim Cook until departing some time next year, the company said in a news release.

As the man behind the system that ran Apple's industry-changing iPhone and iPad, Forstall had been considered a favorite to replace Jobs as CEO after Jobs' death last October. More recently, Apple observers pegged Forstall, 43, as the next in line behind Cook.

Along with marketing chief Phil Schiller and design guru Jonathan Ive, Forstall anchored the company's top tier of executives, frequently speaking at Apple's heralded product unveilings to showcase the ins and outs of operating-system upgrades.

Many felt he was the most logical choice to continue Jobs' legacy of innovation at Apple, where 70% of revenue now comes from the mobile devices that iOS powers.

The Apple press release did not say what Forstall plans to do when he leaves the company.