Ya speaking of 700 years before christ of course, that is just non sense.
Funny how you convince yourself this way when it is clear and very obvious. Yes God spoke to the house of David, and the sign is that the child will be born and this sign will confirm that God will destroy the enemies of Judeah.
The sign is fullfilled if you read before chapter 7 and after chapter 8, and you will see that the child have been indeed been born, and before he learned how to cry or whatever, those enemies were defeated.
What common sense would this make if this child is to be born 700 later?