In chapter 2 of his book The Challenge of Jesus: Rediscovering Who Jesus Was and Is, Wright is exlporing some Messianic ideas held in 1st Century Israel, with some attention to the effect the Messiah would have on the world beyond the nation of Israel herself.
When Israel's God finally does for Israel that which he has promised, then, in much Jewish thought, the effects will ripple out to reach the whole world. The coming King, in many Old Testament texts (e.g. Is 42), would bring God's justice not merely to Israel but to the whole world. Many, said Jesus, will come from east and west and site down with the patriarchs in the kingdom of God.
That last sentence is referring to Matthew 8:11. With the Bishop's next sentence comes the point of interest:
Jesus does not appear to have said much else on this subject.
This statement of Jesus's is one of the few found on the topic in the Gospel texts. As Wright continues we see why this is of interest.
(This is in itself an interesting sign that, despite much current scholarship, the writers of the Gospels did not feel free to invent all kinds of new sayings to suit their own setting and place them on Jesus' lips; the church was heavily involved in the mission to the Gentiles and its attendant problems, but we would hardly guess this from the Gospels.)
In the Book of Acts we see that, indeed, the church is very much on mission to the Gentiles, notably through the work of the Apostle Paul, and that this mission was not without, as Wright says, its "attendant problems". From the earliest account in Acts of the apostles' reaching out to the Gentiles in chapter 10 with Peter and Cornelius, we see the frictional nature of this issue:
Now the apostles and brethren who were in Judea heard that the Gentiles had also received the word of God. And when Peter came up to Jerusalem, those of the circumcision contended with him, saying, "You went in to uncircumcised men and ate with them!" Acts 11:1-3
We also see in Acts 15 that such problems persisted, later concerning what of the Hebrew cultic tradition was expected to be assumed by converted Gentiles. Such dissensions were ignited by Pharisaic elements within the church(15:5), possibly on account of the nationalistic convictions of the Pharisees, which would have obviously been ill-disposed to accepting the Gentiles. If such issues existed, as the New Testament certainly affirms, then authors who, in hopes of giving power to the apostolic fathers, inserted statements into the mouth of Jesus of Nazareth concerning divinity and other "new sayings to suit their own setting" would presumably have further butressed the apostles' authority regarding what theological contentions they were wrestling with at the time.
This line of reasoning may sound at first like a logical fallacy, perhaps argumentum ad ignorantiam; because it has not been proven that Jesus said these things, He must not have said them. This however is not the conclusion being drawn, or the point of Wright's arguement. Whether Jesus spoke more on the subject is here irrelevent, the point is that it was not included in the Gospel narrative. If we have an author who is trying to give authority to the early church fathers concerning divisive issues that the church was actually facing, this and other such omissions from the sacred text certainly indicate, if nothing else, an author incompetent for such a task.
By the way, if you'd like to see a truly awesome photo of the Lord Bishop, you need only look here.