The document describes a technology that uses an image sensor to detect a user's hand location relative to a touch sensitive surface, which extends to the left and right of an existing trackpad, and the keyboard.
Apple envisioned the wide-trackpad to be a solution to make data input on notebooks much more user friendly and create intelligent palm-rest areas that can differentiate between scenarios in which a hand is simply "resting" and when it is applied to control objects on the screen. While the size of touchpads was traditionally minimized to prevent unintended data input, Apple went the other way and searched for ways to extend it.
The wide-area trackpad never went into production and we have no information and suspicion that this will happen anytime soon. The actual benefits of a much wider trackpad may not have been substantial enough to justify the expense of commercializing the idea, even if the move to 3D and previous patent filings that indicate that Apple could be using light beams for object detection above the keyboard could change that stance. In scenarios that rely on touch input, the identification of "accidental contact when a user does not intend to activate the touchpad" is rather tricky.
