Apple has been warning companies of a short-term iMac shortage and alerts retailers there will be no further stock of the entry level 21.5-inch 3.06Ghz iMac, according to Appleinsider. Apple is advising retailers to sell through their current stock of iMacs, which could mean an iMac refresh is coming.
This is a very familiar move by Apple to sell out existing stock of an item, and announce and release a new product with a little as a day notice of a new product. Apple performs these moves so customers won't hold off on purchasing their out-dated products for this years model. The usual procedure for such events is for Apple to announce a press release date, and moments before Steve Jobs takes the stage, the Apple Store temporarily goes down.
There is some speculation on what we could possibly be seeing in the coming weeks from Apple and their new lineup of iMac. According to sources close to the situation said Apple might be planning on releasing a line-up of iMacs with Intel dual-core Core i5 and i7 processors, as well as quad-core Core i5 and i7 models. There is also rumors Apple might be planning on releasing Intel's Core i3 processor, near the more affordable price-point for consumers.
Others speculate Apple might be releasing these all-in-one iMac machines with USB 3.0 support. Although USB 3.0 supported hardware is still relatively new, Apple releasing more innovative iMacs wouldn't be all that surprising.