The end refers to the end of the present heavens and earth in view of what Paul said about it here. This will come more than1 ,000 years after the Rapture. Then Christ, who will have been reigning over His earthly millennial kingdom, will turn over that reign to His Father. Christ"s abolition of all other rule, authority, and power will take place when He subdues the rebels that rise up against Him at the end of the Millennium ( Revelation 20:7-10). He will also defeat death, and from then on no one will die. The saved will enter the new heavens and new earth to enjoy bliss with God forever while the lost will suffer everlasting torment ( Matthew 25:46; Revelation 20:11 to Revelation 21:1). [source][source][source]
"Many see evidence of the millennium in Paul"s discourse on resurrection ( 1 Corinthians 15 , esp. 1 Corinthians 15:20-28)." [1][source]
". . . it is not only possible but probable that Paul understood this final triumph to take place during the millennial reign of Christ. To sum up the principal evidence, Paul"s use of epeita ("after that") and eita ("then") in 1 Corinthians 15:23-24, the syntax of 1 Corinthians 15:24-25, and the parallel use of Psalm 8 , 110 in1Corinthians15 and Hebrews 1 , 2all point to the understanding that when Paul mentioned a kingdom and reign in 1 Corinthians 15:24-25, he referred to the reign of Christ on this earth following His return and prior to the eternal state, a time that Revelation 20:4-6 calls "the thousand years."" [2][source]
Even though Jesus triumphed over death in his resurrection, believers still die. Therefore we must experience resurrection because we are in Christ and because only then will the final enemy, death, be subdued. Only then will God become all in all (i.e, everything that matters; cf. Colossians 3:11). [source][source][source]