This is a not improbable outcome of the future development of digital publishing. Mike Cane is thinking pretty far ahead here, it’s worth reading and thinking about!
Oddly enough met someone today whose vision it is to make sure these kinds of problems go away for digital content and digital intellectual property.
In five years, the contract Publisher A had for the book expires. Publisher A no longer has the right to offer that book.
The way lawyers work, Publisher A will have to remove that book from its servers.
Your book goes POOF!
This should not happen.