Cook will continue on as Apple CEO through the summer, with Ternus set to join Apple's Board of Directors and take over as CEO on September 1, 2026. Cook is going to transition to chairman of the board at Apple, and he will "assist with certain aspects of the company, including engaging with policymakers around the world."
Honestly, I hope it's positive, because Tim Cook has presided over a pretty big drop in quality in terms of macOS releases. With a few notable exceptions, since Steve Jobs died, the changes to macOS have more often been changes to be dreaded instead of looked forward to.
And the operating system's consistency has gone to hell.