Current UAV's can really only be considered to be in the same category as motor cars of 1910... showing tremendous potential, but with a long way to go before all the bugs are ironed out.
The UAV field is further complicated by the sheer variety of "UAV's" appearing. All these will complicate matters until numerous interaction and control issues are solved.
Projects such as CICADA, WASP, VOYEUR, & MAV are all promising projects, but they still need a lot more development work before we see them taking over from piloted aircraft.
CICADA -
CICADA Micro-Drones Opens New Opportunities for Future Covert Surveillance | Defense Update
WASP -
Missile or UAV? UVision Introduces the WASP | Defense Update
MAV -
Miniature Aerial Vehicle (MAV) - Class I UAV for the Future Combat System (FCS) | Defense Update
T-HAWK MAV -
T-Hawk Micro-Aerial Vehicle (MAV) | Defense Update