I’ve waited for the western release of Lost Ark for a long time, and being told the wait for my MAIN, could be potentially longer than the initially expected 2-3 months, has been really demotivating. 
Hope you rethink this and release the classes earlier, i understand u might not want to push too much “content”, but in a game that heavily pushes you to play multiple characters, has an established pvp meta around all of the classes being playable, AND a limited amount of characters you can have on a roster and needing to PAY for additional spots, I think its really sad having to wait this long.
For me currently i have 2 open character slots on my server, and since i want to save these slots for the upcoming classes they are just gonna stay empty until the missing classes are released.
The amazing class design is the main reason i find the game fun, and exploring new classes on my alt characters has been biggest fun factor for me.