This is the 10809th most frequent Korean word.
그때까진
"Until that time."
The word '그때까진' is used here to specify an upper time limit which is being referred to in discussing an event or condition.
우리는 그때까진 만나본 적이 없었어요.
Up until that time, we had never met.
In this instance, '그때까진' signifies a point in the future up to which an action (waiting) is being considered.
그때까진 못 기다릴 것 같아.
I don't think I can wait until then.
The usage of '그때까진' here implies a deadline by which a task or activity should be completed.