In Christ, Israel includes both ethnic Jews and believing Gentiles in one tree. The tree is Israel, it is the people of God in every age. To limit it to a bioethnic group is contrary to the New Testament which in many places takes pains to completely obliterate distinctions between "Jews" and "Greeks". The same kind of mistake is made when "the Church" is understood to be a "Gentile" entity and "Israel" a "Jewish" entity, the two not being reconciled until the end of days.
I am certainly not limiting the olive tree to one bioethnic group since the church has since been grafted in. We are both partakers of the promise, however, there is a clear distinction regarding the fulfillment of the end of days. For example, have you wondered why it is so important that Jesus be of the line of David? Both Mathew and Luke wrote the geanologies to prove it.
The Bible says that the two ARE one, not that they shall be made one.
No. The bible certainly does not state that both are one. There is no Jew nor Greek in the church, however, there certainly is both Jews and gentiles in the end of times narratives. Both the Jews and Gentiles will not be one until the filfillment of the end of times. Until then then there certainly will be those in the church and those that are from the future remnant of Israel.
Such distinctions are the products of a false, superimposed theological imperative.
Brother, not everything has been fulfilled yet. There is still much to come.
The predominance of the expression "Israel" to describe the people of God in the Old Testament, and the predominance of the word "Church" to describe the same people in the New Testament should confuse no one. They are the same thing; i.e. the People of God, the Elect. It is not for nothing that Greek translations of the Old Testament call Israel, gathered for war or for worship, "Ekklesia".
Again, those that are in Christ are certainly part of the church, however, those Jews that composed the remnant of Israel that will be saved in the end of times certainly is not. You need to remember that israel was elected also just as we have. God does not unelect His elect.