For 1978 authors — who are eligible to reclaim in 2013 — the window is already closing.
This is the main point I think 5 years ago many authors would not have thought they have many choices apart from renewing their contracts with dead tree publishers. Now that ebooks have entered mainstream and the ability to self publish available to these authors we might see more back list titles. I hope many of them do take back their rights as authors are way more likely to make sure their ebooks are properly proofread etc. And some of them will be willing to sell at cheaper prices as they wont have to share their income with the publishers.