RE:Isil vs. Bagdad....Far be it from me to predict the behaviour of bunch of renegade terrorists. I have no doubt they would pull a Sadddam Hussein and light up all the oil fields and destroy refineries if they were driven out of the city or unable to sell the oil.
All I know is that people in the mideast feel that ISIS is far too big an organization with far too large of an army to be eradicated with air power alone. Wars are never won with just air power. As long as Obama refuses to put boots on the ground, ISIS will remain a very grave threat to Iraq.