Earlier quoted context omitted.
I think unmanned systems will augment, rather than replace manned airplanes. In one way of thinking, we've been using drones for decades...a tomahawk missile is an unmanned vehicle with a warhead.
I'm sure this is a dumb question but why is it preferable to have a pilot in the cockpit if you could keep them on the ground?
There is research on planes that could be sent off with orders and not require continuous communication, avoiding some of these issues, but to my knowledge they aren't in widespread "production" use.
An F-18, on the other hand, is an engineering marvel and extremely responsive, agile, and flexible. Pilots can react very quickly to situations and have a realistic chance of winning dogfights with other fighter jets, for example, which drones almost certainly couldn't do.
On the other hand, if all you need to do is assassinate some people in a country without an air force, a drone will do just fine.