The A-10's job seems to have evolved into a force protection role. Infantry gets into a jam, A-10 rolls in, hits whatever the enemies last know position was and loiters around while the Infantry either finishes up their business or gets away. The A-10 is cheap to fly, easy to train and carries enough ammo and fire power to get this kind of mission done efficiency. I'm sure what ever they replace it with will be way more expensive to operate and and will require a great more training to fly. It could be a deadly marvel or it could be fiasco of overspending and unattainable technical ambition. I doubt it will be the F-35.
Please correct your post. The A-10 is not a plane. It is a massive stud gun that someone put wings on. About 42 rounds a second? Insanely massive rounds? The average recoil force of the gun is apparently 10,000 pounds-force which is slightly more than the output of one of the A-10's two engines. So with only one engine, it can not fire its cannon without risking a stall I guess. Weak! :) edit: Video footage of the gun firing.