My perfect interface of the future would mix parts from everything.

The ability on MacOS to search the top bar menus just by starting typing
The OS is made of interoperable component, this has been tried so many times but always involves complex things like object models and rpc, I'm not sure how this would unfold
Graphical interfaces should be used for configuration if we're interacting with "objects". This makes much sense when configuring units files (services) or when configuring the network (every port is an object) or firewall rules.
Other simple configurations, key/value pairs could be text.
We shouldn't miss the ability to script things up, and the pipelining. This could be something like plan9 does or it could not.
There should still be a cli, but I'm not sure if it would be the same as it is now. Maybe you could spawn a cli over a running program to interact with it on the fly, or spawn a normal cli system wide.
When running over the network I'm not sure of what would be best, should we rely on form filling (web-like apis) or should we use cli or should we use remote desktops.

Some of those could possibly be implemented on any Unix-like OS as it is now, some would need a bit of fixing.

Just some random ideas thrown around.