GUI is a very powerful advance in the use of computing, and it was originally Xerox who developed this technology, who then sold it to Apple. Given that computers breaking out into mainstream requires greater ease of use, I see either a butterflied GUI emerging from a different and more modern origin, or computing as we know it butterflied away.
Could we see a phone menu style of interface based on voice recognition (Audio transmissions?) Could biometrics and the whole mental user interface take its first steps in development, perhaps on something like a Wii like model?
Humanity isn't going to put up with DOS if better options are available. And, frankly, even if the GUI is shut down different avenues of exploration will begin. I guess the lead rivals at this time would be virtual reality--based on movement, and perhaps something along the likes of video games using controllers. It's hard to imagine the Atari 2600 leading to modern word processing, but its equally hard to imagine GUIs never appearing.
I certainly agree that it is going to be difficult to keep up a command-line interface indefinitely. You did sort of allude to phone menu-driven interfaces, and this is something I was thinking of- consider that console games tend to use a menu-type interface as well. Another possibility is conidering the old style DOS shells and programs- you still might have drop-down menus, and/or functions acessed via keystrokes. Whether this is going to be any easier- remains debatable- even if the shell and other utilities which do not require the command lines are seamlessly built into the system. Remembering all the keystrokes is no different from remembering all the commands, plus there is the usual "finger gymnastics" required when holding down several keys and pressing another.
As for controllers, I suppose you could as a keyboard alternative, develop some more generalised us out of a joystick or gamepad. Another alternative might be a touch-screen type interface, and additionally for graphics, a graphics tablet or light pen. I doubt virtual reality will necessarily work- especially for an office environment, plus people are very much going to be tied into the sit-behind-a-screen model of computing. Voice recognition is a possibility, either for commands or menus, but is not without its drawbacks (training the system to recognise your voice or programming it to underestand any voice, and get it right all the time).
Another possibility is to make the command line more user-friendly by means of more intuitive commands. This obviously was limited by the amount of memory (and possibly processing power) in early systems, especially external commands running utilities restricted in name to the 8.3 format. Plus the way in which single-letter parameters and switches, and the use of wildcards "*" and "?" in file names makes it all look like some sort of bizarre code!
So for example if we want to copy all Word documents from our documents directory to the floppy drive. Instead of, say,
xcopy C:\Documents\*.doc A:\
we might have
copy all doc files in C:\Documents to floppy
or similar.
We also need to make them "idiot proof" so that exact syntax without variations is not necessary, and that the system prompts you if you make a mistake or ned to include something else. For example, consider this:
>copy all doc files
Where?
>To floppy
Which drive?
>A
Where on A drive?
>Root directory
Or say we want help:
>Help
What do you want help with?
>how to copy doc files to floppy dirve
(Help utility provides answer)
You could then adapt this more easily to voice recognition, too.
