My speculation
Putting aside all of the fuzzy sasquach iMac photo's and the like...
I do recall a few months ago (maybe longer) saying that a useful desktop form factor would be an LCD flatpanel "All in One" iMac implimentation:
...think "Pizza Box" design that's stood upright and has the LCD integrated onto the side.
Technologically, this would be very easy to do -- the total form factor need be no bigger than a laptop with the screen flipped over, "tablet" style.
The only "problem" with doing this with an iMac is in the commonly greater cost for laptop miniaturization components, but that's not really as big of a problem as you might think: they already buy this stuff for their laptops, so having the iMac use it too gives them increased economy of scale - - for every dollar it increases the cost of the iMac, it probably saves a dollar off the cost of their laptops. Besides, between a likely 20" LCD screen and the realative ease of adding an extra 1/2" - 1" of thickness to the pizza box, you have significantly more case volume than inside a laptop to put in a couple of cheaper-but-bigger components, such as a 3.5" hard drive.
As such, I'd not be at all surprised to see the new iMac go into this general form factor, which is what these pictures seem to be trying to infer....if you want a catchy name for it, its not the "headless iMac", but rather the "bottomless iMac".
...and I'll even go out on a limb and say that it's possible that just such an iMac design could be carrying the future Powerbook G5 motherboard, once again for simplified and streamlined parts management to keep costs down. Just one more thing to think about...
-hh