I was on the 777 LAX-MIA flight a few weeks ago, and upgrade didn't clear on the day of departure, so I resigned myself to a battlefield upgrade. Did OLCI ~6 hours before departure time, went to the airport in SFO, picked up my BPs for both flights, was noted as being #1 on the upgrade list with ~6 seats left in J on the 777. Like 30 minutes later I got an email from AA stating my upgrade had cleared. Went to the gate and got a re-printed Bo for J.

So, OLCI doesn't hurt you at all, if X (or R as in my case) becomes available after you check-in and are on the list, you will still get auto-upgraded.