While the rapture will end the church age, it will not end the dispensation of grace. The tribulation is still a part of the dispensation of grace. The previous dispensations ended in judgment, and the tribulation is the judgment at the end of the dispensation of grace. We read of many Gentiles becoming believers during the tribulation. Of course, they will not be a part of the body of the Messiah, meaning the church. However, they will be among the sheep Gentiles at the judgment of the Gentiles in the 75-day interval after the tribulation. At this judgment, it will be determined who will or will not enter the Messianic kingdom.
Even after the rapture, the gospel message will remain the same, and people must believe that Yeshua died for their sins, was buried, and rose again. This is the message people must trust for their salvation even after the church has been taken up into heaven (I Cor. 15:1-4). In addition to the gospel, they will also be receiving the “gospel of the kingdom.” This message says that the Messianic kingdom will be set up once Israel becomes a believing nation.
So yes, both Jews and Gentiles will be saved after the rapture, but they will not be part of the church, meaning the body of the Messiah. They will simply be in the category of post-rapture saints.