The F-35 will never be able to fly low and slow like the A-10...
Some variants can hover but that is a completely different flight characteristic.
Oh believe me, I'm a huge A-10 fan. I kinda just want them transferred to the Army so that the military keeps them around longer. The point I was trying to make though was that the Air Force does have a number of different planes that have overlapping roles.
-For some A2G roles, you need a plane to come in and drop a few bombs on a fixed or spotted position that the enemy is hiding or holding out in, or an armored target that can be spotted by either someone on the ground or from the sky. Any plane that can drop precision guidance ordinance can do that job very well, and the cheaper they can do it, the better.
-Some A2G roles have more fluid battle lines, and this is where the A-10 does a better job; it can fly low and slow to identify these targets while they're moving about and engage accordingly. They call these "Attack" planes for a reason, because they enter battlefields and attack accordingly without necessarily having ground spotters to give them targets.
-Then there are A2G roles like the B1B is doing in the Ramadi campaign where you have an entire army on the ground calling targets. They did that in the Kobani campaign too and it was devastating to ISIS. The US military will also sometimes keep a bomber air born and fly from target to target dropping their ordinance, but bombers are only cost efficient if there are lots of things to bomb. They did this in Afghanistan where they just kept a B1B flying at all times and it would fly from target to target dropping its ordinance.
-There are also A2G roles that require stealth. For instance, when entering a battlefield with known radar positions, the US military will go in with full electronic warfare and stealth bombers and wipe out an enemy's air defenses.
I think the idea for the F-35 is to bridge the gap between "Attack" roles and standard bomb trucks. While the F-35 cannot loiter and fly low like the A-10 can, it supposedly can do a very good job of identifying and tracking targets, even infantry, with its electronics package, allowing the plane to bomb with much greater clarity of what it's seeing on the ground (in a way we haven't seen with 4th generation fighters), and do so from a higher, safer altitude. Attack planes are extremely effective at what they do, but it's a very dangerous job. If you can do the job just as effectively, yet more safely with an F-35, then it becomes a harder thing to argue keeping the A-10's around, because these planes certainly do take battle damage when they're engaging targets.
We'll see how good it is once the trials go underway I guess.