1 Corinthians 15:20-23 (YLT), “And now, Christ hath risen out of the dead — the first-fruits of those sleeping he became, 21 for since through man is the death, also through man is a rising again of the dead, 22 for even as in Adam all die, so also in the Christ all shall be made alive, 23 and each in his proper order, a first-fruit Christ, afterwards those who are the Christ’s, in his presence,…”
Christ means anointed. Jesus was the first to be anointed and begotten of the Holy Spirit. He was the first to be resurrected from death. (Other people, who were “resurrected,” were merely resuscitated or revived. They all died again.) “He (Jesus) is the head of the body, the church, who is the beginning, the firstborn from the dead, that in all things He may have the preeminence.” Colossians 1:18 (NKJV)
Then there are the body members of Christ. True Christians also receive the anointing of the Holy Spirit and are part of Christ. At Jesus’s second advent, the dead in Christ are resurrected. Therefore, in 1 Corinthians 15:20, the dead (saints) in Christ are part of the first-fruits. (Please note that first-fruits is plural.)
After the dead in Christ are raised, anointed Christians still living will need to “make their calling and election sure,” (2 Peter 1:10.) These saints will die and immediately be resurrected, “in a moment, in the twinkling of an eye, at the last trumpet… and we shall be changed.” 1 Corinthians 15:52.
Is there any resurrection that happens after Christ (Head and Body)? Yes, first-fruits indicates there will be after-fruits (the world of mankind). The order of the resurrection is Jesus Christ, His anointed body members, and the world of mankind.
Do all the resurrections (other than Jesus’s) wait until the Judgment Day? Yes, Jesus taught, “He (God) has given Him (Jesus) authority to execute judgment, because he is the Son of Man. 28…an hour is coming when all who are in the tombs will hear his voice 29 and come out, those who have done good to the resurrection of life (the Christ), and those who have done evil (mankind) to the resurrection of judgment.” John 5:27-29 (ESV)
The world’s resurrection will take place during Christ’s reign on earth. This is the time when the willing of mankind will have all that Adam lost restored to them (Acts 3:21). Then Isaiah 11:9 (ESV) will be gloriously fulfilled: “They shall not hurt or destroy in all my holy mountain; for the earth shall be full of the knowledge of the LORD as the waters cover the sea.” Also see Isaiah 35:1-10 and Jeremiah 31:31-35.