Given the gradual blurring of lines between iOS and OS X, Siri for Mac is a pretty safe bet. Now, a new patent filing details what the desktop version of the voice assistant might look like. As previous patents have also suggested, it's going to be a lot more extensive than on mobile.
The patent for an "intelligent digital assistant in a desktop environment" lays out a basic premise that is pretty similar to the Siri you already know. It calls for a voice-controlled assistant that can perform basic actions, complete tasks, carry out searches, and so forth. It'll learn as you use it, and it will try to use context clues to understand what you mean.
As far as the tech that powers it, Siri for Mac would use the same backend server that the mobile version uses. You'll likely see it as a standalone app on the desktop or your dock, ready to spring into action when you click it, or it might hum along in the background, waiting for you to wake it up by saying "Hey Siri."
Where it gets more advanced is the patent seems to imply that Siri for Mac will stand in for a lot of the keyboard and mouse gestures you do now. Apparently, it would be able to do things like copy/paste, or retrieve and move a whole bunch of files at once. In some cases, Siri could even sort files by date or time when they're dropped into the Siri application. All of these advanced controls, however, probably wouldn't be something you'd see in the near future. It's still safe to assume that Siri for Mac is probably coming at some point, but it might not be this intelligent yet. Especially when you take into account how not-good iOS Siri still is. [USPTO via AppleInsider]