Memory safety is likely to prevent a lot of bugs. Not necessarily in the kernel proper, I honestly don't see it being used widely there for a while.

In third party drivers is where I see the largest benefit; there are plenty of manufacturers who will build a shitty driver for their device, say that it targets Linux 4.19, and then never support/update it. I have seen quite a few third party drivers for my work and I am not impressed; security flaws, memory leaks, disabling of sensible warnings. Having future drivers written in rust would force these companies to build a working driver that didn't require months of trawling through to fix issues.

Now that I think about it, in 10 years I'll probably be complaining about massive unsafe blocks everywhere...