I vote not going to happen either, but I would love it if they put enough battery in the iMac so I could move it around the house to another outlet without turning it off.
I wonder if the safe sleep / hibernate mode is enabled on desktop macs...
Probably not but you should be able to enable it easily. Then you can just sleep it, wait for state to save, unplug it. When power is restored the system state is then restored from harddrive.
But probably safer to just shut down and restart when moving.
Why oh why would you unplug your 27" iMac and walk around your house? WOW!
I think in the last revision to the iMacs they give the option of battery power. This is probably possible because of the iMacs mobile CPU and GPU components.
I vote not going to happen either, but I would love it if they put enough battery in the iMac so I could move it around the house to another outlet without turning it off.