As I understand it, there will no longer be an AC school as of FY 08. Any remaining legacy copilots will have to be upgraded in-unit.
Original MPDs upgrade to AC via a ~2 week course called the Pilot Checkout Course (PCO), which IIRC consists of only NVG airland and day/night assaults. Little Rock offers extremely limited numbers of PCO slots at the schoolhouse (Dyess is only getting something like 4 slots total for FY 08) the rest will be in-unit upgrades using the same syllabus. Both the 463d and 317th have developed their own "PCO Prep" programs which focus on systems, left-seat tac, etc.
Still waiting on guidance for upgrading the new MPDs, but that's a couple of years away anyhow.