Tracker-4.5.0 has been released as the official/stable version for rovers and boats and should appear in the ground stations (MP, QGC) within the next few hours. Alternatively (once the build completes) it can be manually downloaded from firmware.ardupilot.org.
There are no changes vs the final beta (4.5.0-beta4). For more details on the changes since the beginning of beta testing please refer to the ReleaseNotes.
Thanks for all the developers and beta testers who contributed to this release!