When Paul wrote Rom 11:25-27
For I would not, brethren, that ye should be ignorant of this mystery, lest ye should be wise in your own conceits; that blindness in part is happened to Israel, until the fulness of the Gentiles be come in. 26 And so all Israel shall be saved: as it is written, There shall come out of Sion the Deliverer, and shall turn away ungodliness from Jacob: 27 for this is my covenant unto them, when I shall take away their sins
The All Israel that shall be saved is not the physical nation of Israel, but Spiritual Israel, the Body of Christ, comprised of Abrahams Spiritual seed of promise, consisting of jews and gentiles. So in this manner, by the calling in of the Gentile Elect, Sheep together with the jew elect sheep, all Israel shall be saved, the Body of Christ !