You should unless BA moves you. I was once told by an AA check-in agent (not sure how true it is) that AA can't change seats on BA so BPs are issued automatically with whatever seats BA assigned. So, since you have your 64K pre-assigned you should keep it. The only time I lost a pre-assigned seat was when we were OpUp-ed to F on the BA segment.

Do let us know how it turns out and have a safe flight!