LOL @ "gorilla arm"
Touch will take over.
Maybe not as the primary input mode, but it's nice to touch things at times as it simplifies the process and as the technology is getting cheaper by the day it'll probably be on all screen by default in a few years.
More importantly, the orientation and position of some screens will change to be more touch friendly than a big vertical sitting on the desktop. I could easily see the future desktop computer literally being the desktop, like the original Windows Surface, which eliminates the silly gorilla arm concept.