Consider:
Mary's not here. She'll be at a meeting downtown all afternoon. I guess I'll just have to wait until tomorrow and have her help me then.
A: Ms.Jones left right around 3.00. B: I'll have to call her home, then. This report can't wait. We have to talk about it before tomorrow.
A: We're playing tennis this afternoon. Would you like to join us?
B: Thanks, but I'm really wiped out.
A: Then you'd better rest.
Does then in topic 1 and topic 2 have the same meaning?