The old question of "what happens when Linus/other senior kernel dev dies" mattered far more like 20+ years ago than it does now. The kernel developers are organized quite well, Linux is in general an extremely well-organized open source project these days, and there are several who could fill in. Linus' "2nd" is Greg Kroah-Hartman, who is the lead maintainer of the stable kernel branch (i.e. the one most are using). Linus is the lead maintainer of the in-development branch.

But of course we hope that Linus continues doing this for a long time. Most people never create even one world-changing technology, Linus casually created two (Linux + Git).

Then we fork Linus and continue as usual.

We'll just train an AI from his mailing list posts and continue as usual.

He just turns into a Zombie Process and keeps going

Creating a kernel is hard, Linux itself is not going anywhere.
If all current maintainers suddenly disappear, several corporations, who heavily depend on Linux, will maintain their own forks, so we will get Google kernel for phones, Amazon kernel for datacenters, Valve kernel for gaming, and probably some European initiative kernel for PCs and laptops to do document editing.

We gonna fork him into isekai world!

Greg Kroah-Hartman will take up the role then. He has filled in for Linus in the past.

all linux devs just gonna apply to microsoft

Someone else will take it up. Hopefully the transition is a graceful one, but it could be forked if necessary.

What's the future of you? Linux probably has better chances 🤣