Sadly TERA has not a big future if things don't change drastically. And spoiler alert, things will not change drastically.
There are a lot of people that are interested into TERA's PvP but there are also far to many problems with this game. My PvP Youtube channel has only 13 videos but has 1200 subs and the view count is crazy high for a TERA Corsairs' only channel. This alone proves that TERA has huge potential. I planned for Skyring, Fraywind, in-depth guides/analysis etc. but due to the overall PvP situation i stopped making videos. My goal was 13 videos anyways (each class 1 video), and i reached that personal goal. Once TERA is no more i can look back at my 13 characters from time to time.
Here is the link if you want to check the channel for yourself: https://www.youtube.com/channel/UCWy5TaHS37c4-gY7tmVoz0A
But like i said... there are problems.
1.) TERA is a MMORPG.
You need to max level a character before you can enter PvP battlegrounds.
People that are not interested into MMORPG's wont play TERA no matter how good the combat system or the PvP modes are.
These people want to download the game and start PvP-ing without leveling a character through some MMORPG PvE content. MMORPG's will never ever have huge player numbers like other multiplayer games where you don't need to level up a character first before you can finally play vs. other players.
2.) The game is not optimized very well.
3.) PvP accessibility is in a horrible state, it can't get much worse.
In a perfect world the koreans would just sell the TERA IP to a smart & big game developer (Epic Games, Blizzard etc.). From there TERA would continue existing as a clean PvE game by deleting all PvP battlegrounds.
TERA 2, a PvP only game would be developed in Unreal Engine 5. You can pick a race, class, appearance and the name for your character and you are set for instant PvP action. The combat system would ofc stay the same or if possible be polished some more. Game modes would be Battle Royale, 1vs1, 3vs3, 5vs5, FC, CS for example.
It would be a F2P game without P2W elements and with a battle pass & purchasable skin system. Trade Broker system as we know it should be a thing too so that you can buy items with ingame gold/credits if you don't want to use your own cash. There would be of course much more things to do in TERA 2, it would not be a empty game. Gearing and Glyphs for example would make your characters versatile and only minimalistically stronger. Just so that new players don't have a huge disadvantage when they start.
Imagine having TERA 2 (or whatever the name would be) as an optimized UE 5 game + PvP only game + combat system that is already superior + high play numbers.