Predictions: The strategy of exhaustion can go on for another few decades.
Expect wrangling now about the chain of custody of the pre-1923 editions. The burden will be on the challengers of the copyright to prove that those editions are not later forgeries nor altered in any way. It’ll be fun to see librarians cross-examined about whether their collections have been locked in vaults with secure inventory control for the last 92 years.
And then it will turn out to be that all the copyright licenses were simple quitclaims. Given the duration of the controversy - I’m sure I remember hearing about it forty years ago - I’d be astonished if the licenses aren’t simple agreements not to sue and specifically disclaim asserting that the copyright is valid. So, “no, we don’t own the copyright. We didn’t claim we did. We just got money because we’re big and scary and it’s entirely reasonable that everyone on the planet might want to pay us to keep our lawyers off them.”
And on top of that, whatever the court finds will be valid with respect to only the parties in this suit. "Warner asserted improperly that the copyright was valid. “We do not reach a decision on the validity of the copyright, but find that the specific assertion was improper because…” leaving the door open to the next nuisance suit.
