There are many factors that go into releasing new content and determining if we can grant a new version or old content for free, licensing agreements, etc. Many of these factors are outside of our control.
In addition, each agreement for content is independent and there is no universal policy regarding pricing of new content nor any discounts, refunds, or any other concessions for older content. 

When and if an item is replaced, rescanned, Retired, or moved to Legacy, information regarding that particular item is typically posted in the forum and always in the release notes.