Had a recent positive experience with GS agent who very quickly opened up PN space to force Y->J for me as a companion to GS on a paid J fare.

His travel plans have unexpectedly changed so has to stay in Europe a couple of extra days but I will travel back to US on the originally booked flight. Am I right in thinking that when he changes his flight, I will lose the upgrade and revert back to being on the waitlist for Polaris (since there is no open PN space)?