"Memory, AirPort Extreme and internal Bluetooth upgrades MUST be performed by an Apple Authorized Service provider; fees may apply."
...my caps -- from the Apple Store website.
That's all that anybody knows at the moment.
Until someone turns up here or elsewhere saying that they changed the RAM themselves, that's the truth of the matter.
If it was I'd either postpone that order, up the RAM from Apple, or be happy with what you've got...