In a major leadership announcement that has sent ripples across the global tech industry, Apple confirmed on Monday that long-serving chief executive Tim Cook will step down from his post this coming September, handing the reins of the $4 trillion company to seasoned insider John Ternus. The long-awaited announcement puts to rest years of swirling speculation around a leadership transition for 65-year-old Cook, who will transition into the newly created role of executive chairman of the board after leaving the CEO office.