“We know that that, as Gentiles, we will be in heaven with our Savior, but our Lord and Savior will also reign in the new Jerusalem. Will He be in both places at the same time?”
In the eternal state, the Lamb will have a throne on the new earth and will reign from the new Jerusalem (Rev. 21:1-3; 22:1-3). At the same time, Christ’s throne in heaven will remain forever (Rev. 4:1-11). But Christ won’t physically sit on either of those thrones at all times. Christ’s thrones in both heaven and earth teach that He reigns over all things in the eternal state. The Body of Christ will reign in Christ from our eternal position in the heavenly places (Eph. 2:6), while believing Israel will reign in Christ from their eternal position on the new earth in the new Jerusalem (Rev. 22:5).
Part of Christ’s loving sacrifice for us is that He is the God-man for eternity, the “one mediator between God and men, the man Christ Jesus” (1 Tim. 2:5). As God, Christ is omnipresent, but as a man, like us, He is in one place at a time. The Lord will not be confined to the earth in the eternal state. But when Christ is on the new earth with Israel, we will still experience the fullness of His indwelling presence as we reign in Christ in the heavenly places (and vice versa for Israel when He is with us in heaven). Our apostle reminds us Gentiles in the Body of Christ that we have the blessing of “Christ in you, the hope of glory” (Col. 1:27). We are in Christ and Christ is in us for all eternity. source