I've never understood the rationale of the "two pins, same category" rule. If you rate it, you rate wearing it, what the hell does the "category" matter?
Well, anyway. The deal with the CAC wings is that they're sort of an "upgrade" of the regular Aircrew wings. As the name suggests, once you've served as an AC in combat, you rate wearing the CAC.
So I think what Socrates is asking is, if you've earned the AC wings as a prior, then get comissioned, then fly in combat, can you still "upgrade"?
My answer would be, if you're flying as a pilot or FO, I doubt it. You're no longer serving as an aircrew, so you wouldn't really rate the CAC wings. If you were an officer and part of a flight crew in combat but not as a pilot or FO - though I can't imagine any position in the MC where you'd be doing that - one could make the argument, I guess. Just don't strech the point to a technicality.
The Navy no longer awards CAC wings, but they do allow Sailors who earned them while serving with the Corps to wear them. Usually, that's docs who were already Aircrew and were assigned to a Marine squadron. There was recently an HMC around P'cola who earned them in Iraq.