Even better would be a UAV that could loiter above AA systems and kill at will. They wouldn't hear it coming, much less see it.
We hear they are working on invisible aircraft surfaces, even a report awhile ago about an invisible harrier jet. The guy couldn't see it, even in broad daylight, but could sure HEAR it. Be as it may, these LAB wonders are all very fine, but 5-10-15 years to deployment doesn't cut it, they are needed NOW over there, not "someday".