I guess things are going into that direction naturally, but not officially. eBPF is helping with getting deep kernel aspects into userspace. And there's some ressurgence of out-of-tree graphics drivers, specially for gaming.
I believe userspace drivers are much more powerful and easy to build than 10 years ago, but it is not from a requirement from the kernel.
Who knows, maybe we will get a smaller (instead of bigger) kernel in 10-20 years
Luckily I'm not a kernel maintainer, but it seems like they don't have 10-20 years to make hard practical decisions. It's easy to get rid of old unmaintained drivers, but they have to solidify interfaces much more as it is getting exponentially easier to find and use bugs or any unspecified part of the kernel for attacking it.
There was a very interesting point when people who were creating Rust interfaces were asking hard questions about ownerships and lifetimes in driver interfaces from the C linux maintainers and they didn't really care to answer (just wanted to wish Rust away).
Now with AI these questions are getting practical. Fortunately big companies have big stake in keeping linux secure, so I'm not worried about it being addressed at least.
I believe userspace drivers are much more powerful and easy to build than 10 years ago, but it is not from a requirement from the kernel.
Who knows, maybe we will get a smaller (instead of bigger) kernel in 10-20 years