A super hornet for CAS is a bad comparison - between the two, the F-35 will do much better (standard caveat: in a few years). You're not going to "truly replace" the A-10 with anything that's not a specific CAS/CSAR aircraft. Problem is we're not in any financial position to afford niche aircraft; as shitty as it is, that's the truth. I hope that changes in the future, but it's going to be a while, if it ever happens.