We need to build operating systems from the ground up in languages like Rust. We also need to let go of the UNIX way of doing things and move beyond it. It cannot possibly be the best there can ever be.
Build them for modern hardware and even more so future hardware we can see coming down the line. Build them with security in mind from the ground up. Things like ransomware could be made close to impossible by an operating system.
What will that be? I am not sure.
I am hoping for a lot of people to try a lot of new things and allow things to evolve.