No matter how good a keyboard we might be able to invent it'll always be slower than a direct brain interface, and we have those, in a highly experimental way, now.
One day we will look back at improvements to keyboards and touchscreens as the 'faster horse' of the physical interface era.
I'm not convinced, because all a keyboard really costs you is latency, while almost every human-machine interaction is actually bandwidth limited (by human output).
Even getting zero latency from a perfect brain-machine interface would not make you meaningfully faster at most things I'd assume.
Yeah I noticed this as I became a faster typer. I very often find myself 'buffering' on choosing the right words / code more than I do on my typing speed.
One day we will look back at improvements to keyboards and touchscreens as the 'faster horse' of the physical interface era.