When a new Magento 2.x version is released a merchant can upgrade immediately
When a new Magento 2.x version is released a merchant needs to wait for extension providers/ SIs to assess what changes have made it into this release
Currently it seems the only time a module's version number can change is when the Magento 2 project releases. From an external developer's stand point a better approach would be for the modules to change their version number the moment a version number affecting change is merged into develop. This allows an external developer to follow development between releases without having to wait until the final avalanche of version number increases on release day and then having to play catch up with all changes in a short period of time.
As a further suggestion the following policy would help extension developers prepare for an upcoming release:
At the end of the penultimate sprint before release a Release Candidate is tagged (or earlier). From there until final release only patch level fixes are allowed on the Magento module level (if a fix is required that is breaking a new Release Candidate would be added).