In a certain light, you could argue that Linus doesn’t really have any control at all. He doesn’t write any code for Linux (hasn’t in many years), doesn’t do any real planning or commanding or managing. “All” he does is coordinate merges and maintain his own personal git branch. (And he’s not alone in that: a lot of people maintain their own Linux branches). He has literally no formal authority at all in Linux development.

It just so happens that, by a very large margin, his own personal git branch is the most popular and trusted in the world. People trust his judgment for what goes in and doesn’t go in.

It’s not like Linux development is stopped because Linus goes offline (or goes on vacation or whatever). People keep writing code and discussing and testing and whatnot. It’s just that without Linus’s discerning eye casting judgment on their work, it doesn’t enter the mainstream.

Nothing will really get slowed down. Whether something officially gets labelled by Linus as “6.8” or “6.whatever” doesn’t really matter in the big picture of Linux development.