With DSpace 3.0, the DSpace Developers will be changing our release numbering scheme. Release numbers will now only consist of two numbers: major.minor (e.g. 3.0, 3.1, 4.0):

• incrementing major will represent a new MAJOR release. A major release may include new features or more significant changes/improvements. For example, "3.0", "4.0", "5.0" will all represent new major releases.
• incrementing minor will represent a new MINOR release. A minor release will only include bug fixes to the previous major release. For example, "3.1" and "3.2" will represent 'bug-fix' releases to the "3.0" major release.

For more information see: Release Numbering Scheme