bkuhn pointed out to me (face-to-face, some years ago) that once someone is out of compliance with the GPL 2, there is no formula for getting back the rights they forfeited.
If the copyright holders agree, the formerly uncompliant entity might be granted the original rights as part of an agreement. But technically all copyright holders have to agree for this to be air-tight.
So this is an argument for relicensing to a single entity, one that would do enforcement.
(bkuhn also pointed out that this issue hadn't been a major problem in his experience.)