Tim Cook is stepping down as chief executive officer of Apple after 15 years at the helm, with the company’s hardware engineering chief John Ternus set to take over the role.

The leadership transition comes just one week before Apple’s latest iPhone launch event in Cupertino, where the company is expected to unveil its first foldable iPhone.

Cook took over as Apple CEO from co-founder Steve Jobs in 2011. During his tenure, the company expanded its global operations, shipped billions of devices and recorded unprecedented financial growth.

Apple’s annual revenue quadrupled under Cook, while its share price increased about 20-fold. The company’s market value has also climbed to around $4.7 trillion, making it one of the world’s most valuable and profitable companies.

“Apple is an iconic company,” said Nicolas Sauvage, president of TDK Ventures. “I think Tim Cook moved it to the next level of iconic.”

Analysts had initially questioned whether Apple could maintain its momentum after Jobs’ departure. Cook, however, oversaw the company through major shifts in technology and consumer behaviour while expanding its product and services businesses.

“His biggest legacy is taking over from Steve and then taking it in the direction that went from $300 billion to $4.7 trillion,” said Tim Bajarin, founder of Creative Strategies.

Cook’s departure comes as Apple faces the next major phase of the technology industry, particularly the rapid development of artificial intelligence.

Ternus, who serves as Apple’s senior vice president of hardware engineering, is expected to bring a product-focused approach to the CEO role. He is also expected to lead the presentation of Apple’s new hardware lineup at next week’s launch event.

“The next question really is, what’s Ternus going to do?” Bajarin said. “The fact that he is a product guy and has product ideas makes us hopeful that we may see even new breakthrough products.”

Ternus will now face the challenge of maintaining Apple’s momentum while steering the company through the AI era, following Cook’s lengthy tenure and the legacy left by Jobs.