Look at the recent past
Everyone here is thinking small. If this is true, it's going to be a change every bit as big as the switch to Intel, and maybe bigger. Let's look at Apple's recent history (the last two years):
1. They have killed the XServe line
2. They have deprecated so many features in Lion Server so that it can't be considered a business capable platform anymore.
3. They have removed so many features from Final Cut Pro that the pros, especially the high level ones that drove the sales, can't use it anymore.
Apple has realized that the real money is in content aggregation and sales, not in content creation. It seems that they are systematically killing its high end and content creation products in favor of mobile (and maybe not so mobile) content consumption devices, like the iPhone, iPad Apple TV and the rumored flat screen TV.
Apple isn't stupid. They have recognized the fact that iDevices and iTunes sales are driving their bottom line. Mac sales, even though they are rising, are still only a small portion of the company's revenues. Steve Jobs himself has said that we are entering the "Post PC era", and the writing on the wall is pretty clear. Apple is following HP out of the traditional PC market. The new Mac products (or whatever their name is going to be), will be nothing like the old Macs. I'm guessing that they will be powered by A5 and new "A6" chips, without the ability to run Windows or Carbon apps. They will ship with an updated version of Lion that is more iOS like out of the box, with touch and gestures the rule. They will have small SSD's for the OS and not much else, forcing users to store everything in the cloud. Of course they won't have optical, because that defeats the purpose of the iTunes model, but they will have an SD slot, because that format isn't going away soon.
In short, Apple will introduce computer that is completely consumer oriented and brain dead simple to use.
It will sell like hotcakes.