(I'll) see you then
I will meet you again at the time or date already mentioned or specified. A: "We should probably get together tomorrow to go over the notes before the trial." B: "That would probably be for the best. I'll see you then." A: "Why don't we meet back here in about an hour?" B: "Sounds good, see you then."
(I'll) see you then.
I will see you at the time we've just agreed upon. John: Can we meet at noon? Bill: Sure. See you then. Bye. John: Bye. John: I'll pick you up just after midnight. Sally: See you then.