Just because your older versions are available to users, doesn't mean you have to continuously maintain them. For example, I know plenty of teams still using Java 7, even though Oracle has EOLed it. The teams know the risk that they are taking, and have the flexibility to decide when they want to migrate to a newer version, and that's how it should be. I would never want to live in a world where Oracle can force me to migrate to Java 10 within a day of release.