I just have an outsider perspective, but it seems that he still has to intervene every now and then to maintain a coherent architecture. Could anyone else fill this role, ie. be willing, able and empowered?
As portrayed by tech-media Linus is the main man behind Linux, but for anyone who would even casually follow the LKML, "Linux" is merely Linus' Linux.
If Linus were to cease development, distributions would probably gravitate towards another Linux tree. There is no shortage of trees maintained by very qualified long-term developers who are trusted to keep everything in working order. They're just not as much in the general spotlight as Linus.
Even if different distributors would lean towards different trees, features and patches would be equalised by third parties and another main tree would establish itself as "Linux."
There is a possibility that Linux splits into multiple variants (server, supercomputer, desktop, embedded, ...), but as long as the licences are compatible I see no problem.
Just the other day there was a spat between a security guy and Torvalds, where the security guy wanted to push a patch set that would crash even the kernel if something in userspace made it do something "funny".
And said security guy have a whole bunch of cheerleaders in userspace (quite a few stepped onto social media to defend the patch set and berate Torvalds for being a potty mouthed bully), and perhaps even a few in kernel space.