This; the old books still exist. No one is coming for them.
The copyright-owners have simply decided that the new editions of the books will be different.
Hell, this might even be a simple cash-grab: if the books aren't selling as well now, and their royalty checks are shrinking, they may have done some basic market research and determined that the perceived crassness of the works was turning off modern book-buying-parents, and decided they could make more money with a revised edition.
If you don't like it, there will be thousands, millions of old copies at used bookstores and libraries; most old books don't get new editions, anyway. And if that's not good enough, by around 2060 most of the copyrights will have expired (his work spans the 1978 copyright change), and you can republish them with whatever changes you like to your heart's content.
Sure, and beyond that, my point was, if copyright deposit is working, there are copies in public hands, specifically for the purpose of preservation and availability beyond the expiration of exclusive rights, not just old books in private collectors hands.