There is no doubt in my mind that the new iMac computers will have the RAM soldered onto the logic board. It's the natural evolution of where Apple are heading with their computers. The less upgradeable the computer is the quicker people will need to upgrade thus making more money for Apple.
You will all laugh now but come back to this thread in a month when you're all crying. Then you'll see. It's only a matter of time.
I think this is very likely next refresh. If apple updates the iMac this year with just a refresh, in 2013 they might redesign and I could see them making the imac useless towards upgradeability. Hopefully they will have the old design with updated internals like they did with the mbp.
Lets just see if they even update their AIO and the Mac Mini.