I do not know how many times I have read this and I can not find where it says that the "only" people who have a celestial body are the "saved" and even if I could find that scripture, I still do not see where 50 Now this I say, brethren, that flesh and blood cannot inherit the kingdom of God: neither doth corruption inherit incorruption. Behold I show you a mystery, We shall not all sleep, but we shall be changed....the dead shall be raised incorruptible and we shall be changed.....
You are correct in that, only the saved will be raised and caught up. But as I have tried to explain to you, after the church has been gathered and changed immortal and glorified, the time of God's wrath will follow. During that time, there will people who will become believers in Christ, many of who will be killed on the beasts authority. These are referred to in Revelation as the great tribulation saints. Those of them who are killed during the beasts reign will be resurrected when Jesus returns to the earth to end the age. The following scriptures is the introduction to the great tribulation saints and their resurrection
Note: this group is not the church
==========================================
"After this I looked and saw a multitude too large to count, from every nation and tribe and people and tongue, standing before the throne and before the Lamb. They were wearing white robes and were holding palm branches in their hands."
"Then one of the elders addressed me: “These in white robes,” he asked, “who are they, and where have they come from?”
“Sir,” I answered, “you know.”
So he replied, “
These are the ones who have come out of the great tribulation; they have washed their robes and made them white in the blood of the Lamb.
"And I saw the souls of those who had been beheaded for their testimony of Jesus and for the word of God, and those who had not worshiped the beast or its image, and had not received its mark on their foreheads or hands. And they came to life and reigned with Christ for a thousand years. "
==========================================
All who do not make the 1st resurrection, have to make it to the lake of fire.
The information that you are missing is that, there are multiple phases, or stages that make up the first resurrection:
1. Jesus the first fruits - 1 Cor.15:20-23
2. The church - John 14:1-3, 1 Thess.4:13-17, 1 Cor.15:51-53
3. The male child/144,000 - Rev.12:5
4. The two witness - Rev.11:7-11
5. The great tribulation saints - Rev.20:4-6
All of the above fall under the banner of the first resurrection, each of which takes place at different times prior to Christ's thousand year reign.
Flesh and blood are not going to make it 1000 yrs.
What you are not taking into consideration regarding above, and as I have already made know to you is that, the great tribulation saints will become believers AFTER the church has been gathered. And so they will still be in there mortal bodies. Those of this group who die during that time will be resurrected, also immortal and glorified when Christ returns to the earth to end the age, . Those who make it through the time of God's wrath and the beasts reign alive, will enter into the thousand year reign of Christ in their mortal bodies and will repopulate the earth during the millennial period. According to Isaiah 65:20, The life span during the thousand years will be increased as it was prior to the flood:
"Never again will there be in it an infant who lives but a few days, or an old man who does not live out his years; the one who dies at a hundred will be thought a mere child; the one who fails to reach a hundred will be considered accursed.
All that your quote of 1 Cor.15:50 is saying is that, those in Christ, dead and living, cannot inherit the kingdom of God (heaven) in these mortal bodies, which are decaying and die. And that they have to be changed immortal and glorified, as revealed in the following scripture:
"So will it be with the resurrection of the dead: What is sown is perishable; it is raised imperishable. It is sown in dishonor; it is raised in glory. It is sown in weakness; it is raised in power."
When believers are resurrected and the living believers are changed and caught up, they will take on heavenly characteristics fit for heaven.