I firmly believe in the doctrine of duel fulfillments. So no I'm not going to deny that this is in some way applicable to Isaiah's own time in the reign of King Ahaz, when the Northern Kingdom and Aram Damascus were allied against Judah.
I'll even agree that the Prophetess who becomes Pregnant in Isaiah 8 is a lesser near fulfillment of the Almah mentioned in Isaiah 7:14.
One thing I've seen is that some people think this Prophetess is Isaiah's wife. It's difficult to know for sure, but I've generally more leaned towards the idea that this child in question is Hezekiah and the Prophetess is Abijah also called Abi his mother. And so the Zechariah who is Abi's father is the same as Zechariah son of Jeberechiah mentioned in Isaiah 8:2.
I think the basis for interpreting her as Isaiah's wife is taking the language of 8:3 as literally saying Isaiah fathered the child. But I don't think that is the intent here. It could be Isaiah's personal role in this first fulfillment is played in The Nativity narrative by Simeon or Anna in Luke 2.
My hunch is this Prophetess Office was directly inherited from that held by both Deborah and Miriam the Sister of Moses. Thus backing up aspects of what I argued in the Almah post about the significance of Miriam being called an Almah. And at the time of the Birth of Christ this Prophetess Office was held by Anna of Luke's Gospel.
Maybe at some point it became standard for this Prophetess to be among the wives of The King. Like the ceremonial marriage between King and Priestess many pagan cultures had. The Marriage between Jehoram's daughter Jehosheba and the Priest Jehoiada may have been a similar arrangement, a marriage alliance between the Royal family and the Priesthood.
Isaiah 8:14 is terminology drawn on by Paul (Romans 9:32-33, 11:9 and 1 Corinthians 1:23) as well as 1 Peter 2:8-10. So quoting this promised Son as being Jesus was not unique to Matthew.
The key objection many might have to applying this prophecy all the way into Isaiah 8 to the time of Jesus birth is what's said in Isaiah 8:4.
For before the child shall have knowledge to cry, "My father", and "my mother", the riches of Damascus and the spoil of Samaria shall be taken away before the king of Assyria.I have argued that King Herod died during the 40 days between Jesus Birth and Presentation in The Temple. After he died rebellions broke out in the lands Herod ruled, which did extend to include parts of Old Testament Aram. And these were put down by Varus when he was governor of Roman Syria. I don't think it's that hard to typologically say Rome is in the role of Assyria here. Especially the Roman Province of Syria which was basically what the Seleucid Empire had declined to. And the Greek name Syria is directly derived from Assyria.
Josephus talks in-depth about these campaigns. One battle is clearly placed in the general area of Samaria.
But even if more time separated Jesus Birth from Herod's Death. It can sometimes take a year or two before a child is able to speak. Or that verse could refer to more then just being first able to speak. It could make sense for a Christians to see that point in Jesus development as the Passover when he was 12 that Luke 2 records.
However the argument that Isaiah 7:14 needs to be understood in the immediate context of chapter 7-8 can also be countered by pointing out that they exist in the context of the chapters around them with no clear separation, not ending till chapter 12. Meaning this promised Child is perfectly valid to identify with the Child foretold in Chapter 9 and the Branch of Chapter 11. The overarching theme is foretelling Israel to be carried away into captivity but also that they will one day be regathered by a Messiah.
And in Genesis God made Promised to Abraham, Isaac and Jacob that weren't fulfilled in their lifetimes. So no there isn't a guarantee this promise made to Ahaz had to be, since he himself said he didn't need such a sign.