Im a little biased because my company makes video eyewear (
www.icuiti.com)
and there are several companys now coming out with commercially viable stuff like ours.
once you take the display off a laptop or tablet PC, the size limiting factor becomes the keyboard.
for a PDA it becomes the input device (touch screen or mouse input). It will only be a few years until we have 1024 or 1280 resolution video eyewear, so the direct view LCD will definately be on its way out by then
but I have never seen anything that can replace a keyboard for normal PC/Laptop use
So you still have three distinct sizes of devices:
I dont want a big cell phone, I dont need a cell phone with video eyewear that is required to use it
wearable displays are excellent for PDAs and laptops. Im sure something like the AirMouse will replace the touch screen on PDAs and pocket PCs
but for portable PCs / Laptops, I cant see the touch-type style keyboard going away.
Thats why I see these three functions remaining as three distinct devices for the next several years