Aircraft did CAS long before the A-10 and will do it long after there are no more, it is not the be all to end all. I find it mildly amusing that in this debate is seems to be ignored that the one service that puts the most focus on CAS is also one that has never had the A-10 in its inventory, relying on training and a culture of supporting their folks on the ground coupled with capable aircraft that have proven they can do the job in war. The AC-130 mentioned as the only other real CAS aircraft shows just how USAF myopic the article is.
The article also brings up a few things that A-10 supporters always point out as advantages but might not be as big as they suppose. First off resistance to battle damage, it is great that you can bring a severely damaged A-10 home but a mission kill removes an aircraft from our inventory just as surely as a 'hard kill'. You might have 12 A-10's sitting on deck but only 2 flyable because they the other 10 got seriously damaged needing to get low and slow to make their tank kills. It also ignores the fact that getting low and slow in contested airspace nowadays is a recipe to get blown out of the sky, armored cockpit or not. The A-10 has flown the overwhelming majority of its combat missions in uncontested airspace where it has not had to face modern SAMs, something the F-35 would likely do much better against.
Then there is the gun, while great for killing tanks how much better is it really against some dudes on the ground with AKs? Wouldn't a 20mm would do just as good a job in that scenario? Against tanks? Sure, but then the next place we may find those on the battlefield as a real threat I am guessing the airspace won't be as permissive an operating environment as we have fought in the past 14 years.
Finally there comes the simple fact of age, the A-10 is getting old and that isn't always a good thing for an aircraft. While we have flown some aircraft for much longer, like the B-52 and KC-135, they often have more unique roles that cannot be duplicated in other current aircraft and have not been flown in such demanding roles their entire careers. I would hazard a guess that the amount of stress put on even B-52's their entire career is orders of magnitude less than the average A-1o that are probably 2 decades younger. The modifications, upgrades and monitoring to ensure just the airframes themselves are safe will almost certainly increase over time. Then there is the need to ensure the mission systems keep up to a level where the aircraft can just simply operate along with its more modern brethren in the same airspace and against more modern anti-aircraft threats.
I get the affection and attachment that many folks have to the A-10 but some of its more fervent supporters seem to letting emotion get in the way of facts and simple reality. Sooner or later the A-10 will have to retire, if not now then when and with what? And do we even really need one?