It’s not only the 27-inch iMac that takes a long time to ship but also the 21.5-inch version now, according to the latest update on store.apple.com. The new all-in-ones take between two and three weeks to arrive now.
If you place an order for a 21.5-inch iMac (Late 2012) right now you’ll be lucky if you receive it in early February, but chances are you’ll be getting it a tad later. Apple currently cites a 2-3 week waiting time for shipping.
To be noted that this quota is actually worse than the one before. The systems were previously available to ship in 7-10 business days, so something is happening.
The 27-inch models remain stuck at 3-4 weeks. Apple has previously said that the technologies employed to make the new iMacs were new, thus slowing down production.