Signal Jamming or loss for any other reason can be overcome.
The aircraft would continue flying on it's own for a short time, observing it's route plan/TCAS/WX etc. If after this time, say for the sake of arguement 5 minutes the data link is still down/jammed the the on-board computer changes squark code to reflect lack of comms and lands at the nearest suitable ILS airfield.
The ground control unit will already know which one it's going to land at because they will have programmed the suitable airfields into the UAV and phoned ahead at let ATC know whats happening.
Thegoaf: the technology already exists like you said, and I think within the next 10yrs we'll see the odd light payload cargo UAV making it's first trip. All that needs to happen is the available technology be fitted into a small space and certified by the CAA (or whichever country it will fly in).
PAX aircraft? narrhhhh, 40-50yrs maybe.
Last point: CAP722 published by the CAA details their position on UAV's
