After the recent K-TERA dungeon tournament event was completed, a short trailer was played which announced the opening of a classic server.
Back in August 2018, Pmang ran a time-limited classic server for J-TERA (TERA Japanese server). Nexon will likely follow the same format where the classic server will allow players to experience the game as it was back in the 2014 period, and eventually revert it back to the current day server. The content and game systems will effectively be from just prior to the Fate of Arun expansion (aka TERA: Rising).
Temporarily turning back the clock will allow those heavily into nostalgia, a brief period of time to re-experience things as it was (quirks and all including the lack of QoL improvements and streamlining made since then).
UPDATE: The classic server is now open and is accessed via a separate game client. A leveling event is currently active. There doesn’t seem to be any details if this is a time limited event like it was for J-TERA though or if Nexon plans to eventually treat it as a progression server. I will probably be giving it a try.
UPDATE #2: This is also a time-limited event server that will last until March 14th. Character progression on the event server will be rolled into the main server (items and other content that are no longer relevant will not carry over/be unusable) and gear replaced with suitable current versions.