Originally Posted by stoffe
Then it's time for him to take a one-way trip to Baator to make good on his end of the deals and pacts he made. Unless the player is keen on going there as well they most likely part ways after KOSH is beaten.
I actually don't think AJ would be headed off to Baator - he looks more like he forcibly summoned his army of fiends than made any pacts with them. Mephasm tried to use the PC to run off during the middle of a mission, and Koraboros claims AJ "imprisoned" him and tries to kill him for it. Being law-abiding devils, they'd have remained loyal to him if they/their superiors had made any pacts. Demons I doubt would even bother with any agreements, as they violate then as they saw fit.
AJ could still adventure with the PC, though there'd probably be quite a few vengeful fiends on his tail.
(Though I suppose his fate is sealed, as he's Neutral Evil and bound for the Lower Planes anyway)