Noncommand User Interfaces, by Jakob Nielsen. A view (from 1993) of future developments in UI. Section 4 outlines twelve dimensions interfaces could expand.
I'd not thought about the input bandwidth issue: the computer takes low bandwidth input (a mouse gives you only screen coordinates and type of click) and disproportionately high bandwidth output (video, sound). Is this a bad thing, do we need high bandwidth input too? Not sure. It's the informational equivalent of a lever, a small and precise movement scaling up to a much larger effect. Or a magical word of command, Let There Be Light. Such a small effort (a hand gesture, a phrase, a raised staff) to part the sea. Maybe that's why technology feels so much like magic, because the universe is by default a proportionate place and it's the application of science that gives us levers and commands, informational and otherwise. If it wasn't magical, it would be harder.