For the judgment was accomplished not only upon all the men of the Christian church, but also upon all who are called Mohammedans, and, moreover, upon all the Gentiles in the whole world. ↗
The children of believing parents, at least their next and immediate seed, even of us Gentiles now under the gospel, are included by God within the covenant of grace. ↗
But the Jews will also be believers, so you can say that all the saints, both gentiles and Jews, will go into the millennial kingdom and populate the earth. ↗