It's going to happen
When we make decisions, in any environment, we employ a set of rules. This set of rules is used to determine what the best decision is through a form of risk management. Someone, somewhere, is busily beavering away finding out what those rules are. When he has finished he will have the basis of an AI capable of emulating the flexible mindset of the human pilot, but with all of the data in accurate numerical form available. This AI can be programmed into an appropriate computer which will then be used, on-board, to fly the UAV. Simple if-then statements will do for mission objectives, with more complex routines to cover more difficult manouvers such as air combat, but everything will be essentially if-then based (just like we work). For political reasons, there will likely be a human monitor (not mission essential) who will have the ability to destroy the UAV.
UAV's are unlikely to hit the commercial sector, though, since people are "happier" with human pilots.
Ta muchly
PTT