I guess no one could understand my babbling... So let me put it another way. As I see it from an Full Preterist prespective the Fulness of the Gentiles would have come to fulness at the ending of that generation. Paul spoke of that generation as holy priest hood, the chosen of God, an chosen generation, a royal priest hood, an holy nation, a peculiar people.
Paul would in 1 Peter 4:7 tell them that "the end of all things is at hand: be ye therefore sober, and watch unto prayer". So if one was to take that when Paul spoke of Gentiles coming into the kingdom of God it seems that Paul was saying that it was only for that generation and not for any other. This forces us to rethink about the church of today. I mean if they were to be saved from death and hell and second death which is the wrath of God upon that wicked generation. What then is salvation of today? What are you actually saved from? Seem Paul maded it clear that within that generation would all things come to an end. Thus if the gospel was to go out to the Gentiles if they were pagan heathens it was only for a very limited time (that generation), Then again if Gentiles mean those of the children of Israel from the seed of Ephraim that had been carried away and now know through the message going out unto them would bring them back into the fold, again it's a very limited time. By the time of Christ, centuries after both the Babylonian Exile and the Assyrian Exile, there were still people known from the tribe of Asher. And that some of the Jews asked where was Jesus going...was he going to the dispersed among the Gentiles?
And there was a prophetess, Anna, the daughter of Phanuel, of the tribe of Asher.
Then said the Jews among themselves, Whither will he go, that we shall not find him? will he go unto the dispersed among the Gentiles, and teach the Gentiles?
Considering the northen kingdom captial of Samaria where Israelites lived in the time of Christ and were considered 'dogs' given meaning that they were a 'unclean animal' or 'lowly servants'. The Jews considered them to be under the Curse of Canaan, and to be half-breeds. Jesus said as much and told his disciples to not go unto Samaria, but rather go to the lost sheep of the house of Israel. Well Samaria was the house of Israel, but I gather that we should take what Jesus said as the house of Judah (Jews) Go to the Jews first. We find out later then the gospel was to go unto the Gentiles 'Multitudes' that Philip goes down to Samaria and proclaimed unto them Christ.
So the mystery might just be that the Jews had written off the northern tribes becasue they no longer keep the Laws of Moses, but Paul told them he would not have them ignorant of this mystery that their own blindness has made the way for the fulness of the Multitudes.