In Chapter 11, Paul emphatically notes that God has not rejected the Jews in total as is evidenced by the remnant that remains faithful to the true King of creation. Yet, Paul then takes things in a totally puzzling direction by stating in verse 26 that "all my fellow countrymen shall be rescued." What is he talking about? Dispensationalists argue that after the rapture, tribulation and all the other stuff that has given Tim LaHaye "up yours money" that all of Israel will follow Jesus as King but for reasons that are too involved for this post (which I type in a bed & breakfast in friggin' New Jersey) I ain't no dispensationalist.
Pre-mill Calvinists like Doug Moo argue that 11:25-32 refers to a large number of Jews who will be saved over time (i.e., generations of remnants eventually numbering the whole number of Israelites at the time) culminating in a mass revival of Jews at the time of the return of Jesus. This is certainly a better reading than the dualistic dispensationalist reading that was a product of the twisted mind of a torked English lawyer named Darby.
However, I think N.T. Wright is correct to argue that 11:26 is a reflection of 10:13 (and one must also keep 9:5 in mind) that Paul has redefined "Israel" as the people of God whether they be Jew or Gentile.
Wright's argument is bolstered by Galatians 6: ("May I never boast of anything except the cross of our Lord Jesus Christ, by which the world has been crucified to me, and I to the world. 15 For neither circumcision nor uncircumcision is anything; but a new creation is everything! 16 As for those who will follow this rule—peace be upon them, and mercy, and upon the Israel of God.") (NRSV).
Finally, Wright is also correct to argue that the normal English translation "So all Israel shall be saved" should be rendered "in this manner all Israel shall be saved" to prevent temporal confusion.