It does seam that AA is moving towards standby upgrades only. I had a similar experience trying to get upgrades for a trip from DFW to LGW. When I booked, it appeared that all the J seats were available for the return flight. There were still no upgrades available. I did get 3 VIP04 upgrades to clear for the outbound flight 9 days before departure. I am sill waitlisted for the return flight while the majority of J seats appear to be available.