The upcoming Unity 5.6 will be the latest version of Unity 5. After its release, the engine switches to a new life cycle.
As part of the announcement of beta and Unity 5.6, the developer of the Unity Technologies engine announced a change in the strategy for releasing versions of the engine. After the release of the upcoming update, the engine will lose the numbered part. Updates will be named according to the year of release. For example, the new version after the release of Unity 5.6 will be called Unity 2017.1.
The Unity authors explain that such a release system is better suited for the release cycle: “a date-based version system is more suited to how we work on Unity versions and better reflects our desire for fast iteration and frequent releases.”
The beta version of Unity 2017 will be available in April next year. Developers who bought the perpetual version on Unity 5 will run out of access to new versions of the engine in the spring. They will be asked to switch to a subscription or purchase the “pay-to-own” option, which allows them to stay on the Unity version that was available at that time after the expiration of the 24-month subscription plan.
Source: Unity