"Premium" PE seats - no way to book as non-elite?

Hi,

Trying to sort out this PE thing here...and it appears as though quite a few of the seats (as shown in ExpertFlyer) aren't bookable by any but elites.

Okay, that's fine...but is that always the case? Is it possible that they will open up on the day of departure and I can jump in then? Should I just book seats on the dates I want and hope they'll open up (on upgrades for elites) or just get the best seats I can get now?

Thanks in advance.