After updating to the latest version of FreeNAS 11.2U8 you receive a new message in FreeNAS – Update Train EOL Reached Message
This just means that there will not be any more updates for the 11.2 Train.
As of the writing of this article FreeNAS Version 11.2U8 was just released and you should not have to worry about this right away. It just means that you should plan on making the transition to 11.3 before too long.
FreeNAS version 11.3 is still new and not all of the bugs are worked out and we are still doing testing ourselves. We recommend waiting a few revisions before completely moving over a production unit to the version.