Apple filed for the 'magic trackpad' trademark on February 26, 2010 with the US Patent & Trademark Office according to Patently Apple. 'Magic Trackpad' likely refers to an external peripheral device for desktop computers or laptops plugged into external displays.
With more and more of OSX relying on Multi-touch gestures, Apple will likely provide desktop users a way to take advantage of such a system. Will it be just a trackpad lifted from a MacBook and connected via USB or Bluetooth or will there be more to it than that? Perhaps Apple is referring to a keyboard/trackpad combo?