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.
No it won't the reason it was in the rMBP is because they needed it to be ULTRA-THIN, there is no reason for a desktop computer to be ULTRA-THIN because it is not portable!
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Apple know soldered RAM is no big deal. Away from this forum, what percentage of real world customers ever upgrade RAM during the lifetime of a Mac? I bet it's in the single figures.
Yea I know... a lot of people think about it but when push comes to shove they say **** it!