Yeah, but once they get those paper-thin OLED displays that you can roll up in your laptop bag, the desktop is DOOMED! 
-Deozaan
While that initially sounds good, the fact is that it's not true. Paper thin displays will open up new possibilities for portability, but... The desktop will live forever. Here's the proof inside 1 simple question:
Do you want to unscroll and hold a 24" paper thin monitor on your lap or hold it as you are walking?
Clearly no.
It's entirely about the physical limits of human vision and our need to have sufficiently large display space to easily view things. You can miniaturize computers, but you can't miniaturize humans or conversely increase the quality of people's vision (that's another question though for biotech).
Do you want to play the latest 1st person shooter on a 3"x5" screen? A 9" screen? No. You want a big huge honking mother of a display that covers the entire wall! You don't really want a 24" display... you want a 24' display! Because that's bigger, better, and much much cooler to run down cops and shoot hookers on. Why watch blood squirt 12 mm when you can watch it squirt 12 feet?
The desktop may be reduced to the size of just a keyboard someday, but displays will always remain large.
On a side note, the keyboard is the limiting factor in how small a computer can be until speech recognition and tracking retinal movements becomes popularly viable. It's all about interfacing with humans, and what factors on the human side are limiters.
