In a strategypage article on US Navy's interest in UAVs, we see this:
The U.S. Department of Defense has decided to make the next generation heavy bomber an unmanned aircraft. The Department of Defense also wants the new aircraft in service by the end of the next decade, some twenty years ahead of schedule. [...]
the Pentagon finally got hip to the fact that the UCAS developers were coming up with an [unmanned] aircraft that could replace all current fighter-bombers. This was partly because of the success of the X45 in reaching its development goals, and the real-world success of the Predator and Global Hawk.
UAVs are clearly bringing about a shift in tactics. Computers and unmanned navigation have proceeded to the point where a UAV can take off, fly to target, attack, and return completely unassisted by humans. Furthermore, the loss of fighter pilots is greatly reduced.
UAVs can swarm air defenses as an expendable first wave of any assult.
In terms of combat air support, UAVs can hover over the batterfield, performing 24/7 recon or hitting select targets from the air. The US military uses UAVs in precisely this fashion, in Iraq and Afghanistan.