wow, that is a complex question, actually...... I'm sure I won't do it justice, but I would like to comment anyway.....
The immediate fulfillment of this prophecy was Joshua. He led the people as Moses had, and he was for all intents and purposes God's spokesperson. He had learned from Moses's conversations with God in the Tent of Meeting, and he had served Moses and believed God when he was a spy sent in to the Promised Land. A series of great prophets were given to the people of Israel over the years, notably Elijah, Elisha, Samuel, Isaiah, and Ezekiel, among (of course) others.
I believe this parable to be related: from Luke 20: ... "A man planted a vineyard and rented it out to vine-growers, and went on a journey for a long time. 10 "At the harvest time he sent a slave to the vine-growers, so that they would give him some of the produce of the vineyard; but the vine-growers beat him and sent him away empty-handed. 11 "And he proceeded to send another slave; and they beat him also and treated him shamefully and sent him away empty-handed. 12 "And he proceeded to send a third; and this one also they wounded and cast out. 13 "The owner of the vineyard said, `What shall I do? I will send my beloved son; perhaps they will respect him.' 14 "But when the vine-growers saw him, they reasoned with one another, saying, `This is the heir; let us kill him so that the inheritance will be ours.' 15 "So they threw him out of the vineyard and killed him. What, then, will the owner of the vineyard do to them? 16 "He will come and destroy these vine-growers and will give the vineyard to others." When they heard it, they said, "May it never be!" 17 But Jesus looked at them and said, "What then is this that is written: `THE STONE WHICH THE BUILDERS REJECTED, THIS BECAME THE CHIEF CORNER stone'?
Jesus is the ULTIMATE fulfillment of Deuteronomy 18, as He is the ultimate fulfillment of the entire old covenant.
Interesting: in Deuteronomy 18:16 it says: "This is according to all that you asked of the LORD your God in Horeb on the day of the assembly, saying, `Let me not hear again the voice of the LORD my God, let me not see this great fire anymore, or I will die.'" and then in 1 Timothy 2:5 it says that "there is one God, and one mediator also between God and men, the man Christ Jesus." so Jesus becomes once and for all THE mediator, THE prophet, THE intercessor....
....and we can all enter into this ministry of Christ Jesus -- see Acts 2 and 1 Corinthians 14 -- not to supercede Him of course, nor to replace Him (God forbid!) but because He deigns to allow us to participate! PTL!
blessings
tal