A correct English sentence would read " " Will you have talked by then". I have tried to come up with a situation where the above could make sense but failed.
It's clunky but I think it's legitimate and I have heard it used before. "You need to talk to your father before you fly to Germany. Your flight leaves in the morning. Will you have talked [to him] by then?"
Sped, I think there is a misunderstanding because the sentence using "by" as written above is correct but the phrase I was questioning was " I will have talked until then". To make any sense of this phrase it needs to be accompanied by something like "I will leave at four, I will have talked until then" The problem is that in Eng. by and until have different meanings, they are not interchangeable, "by" indicates a moment in time and " until" continuity. Maybe "μέχρι " can mean either which may be the source of the problem.
Yes, that's right, in Greek μέχρι is flexible and can mean 'until' or 'by', depending on context. Well, that's my understanding of it, anyway. Like most of the prepositions - από, σε, για, etc - it doesn't really translate perfectly and has all sorts of subtle variations in meaning which you can really only pick up via practice.