Now Apple just needs to incorporate this into the "iPad Keyboard Dock" and I'll be more than happy to buy!
That said, it shouldn't. Why would anyone prefer indirect manipulation of a cursor over direct manipulation of the screen elements? If you've got an iPad in a keyboard dock, you're primarily writing and occasionally navigating. I don't see the use case.
Gorilla-arm would only set in if you were primarily navigating, in which case you'd just undock the thing.