The kernel is probably too large to rewrite the whole thing at once. This could lead to a future without any new C kernel devs, leading to stagnation, while the Rust kernel could be many years away from being finished. (Assuming we actually move away from C.)
At that point you might as well just start an entirely new kernel and hope it is good enough to eventually replace the Linux one once all devs are gone. Kinda the X11 and wayland thing.
I’m still waiting for a reason to get a PS5 at all, everything I’ve been interested still got released on PS4 too - except for one single game.
I really don’t care for better specs anymore, I probably couldn’t even tell PS4 and PS5 games apart without a side-by-side comparison. Not to mention, to see a difference at all I’d need a new TV on top of the console. Not gonna happen anytime soon.