So I heard back from Cakewalk support. They sent me a product key for AD2, but unfortunately, it didn't really do much. After registering the key, there was the same functionality in AD2 as the free demo (i.e. there are no drum sounds, just the main AD2 software and a demo of Fairfax AD Pak).
This morning I heard back for XLN Audio Support, who had to reset my licenses for AD2. Now I have the full upgrade, which includes a couple kits that were upgraded from AD1.
So I've got my upgrade now (yay!), but I wish this process had been more smooth.