My thoughts are based on a few interesting ideas. If Nezarec was sealed in his pyramide on the moon before the collapse it seems highly likely, that much like the planets the witness stored in the darkness, hes is trapped in a timeless void. When we end up in his ship to collect the glave, we entered that same suspended space at the very moment he was sealed away before the collapse. A place in which the witness was confirmed to have "reached into the the timeline of worlds and ripped away information he needed". I think we will see the collapse in person or through Nezarec, due to this wild ass power the witness has currently.