It is apparently these non-christian sheep who will be alive on earth after Armageddon when the devil is abyssed - not christians. This will explain why there are still people on earth to be misled by Satan after the thousand years. Christians have "one hope" - the heavenly one. (Ephesians 4:4) Ignorant non christians who are righteously disposed and treat christians favorably, have the prospect of surviving Armageddon.
The basic scenario accepted by many, if not most Christians is that the rapture will come at Jesus appearing, where he meets the church (new covenant believers) "in the air". (not the 2nd coming, but getting close). This ends the "church age". Immediately after this, the rise of the anti-christ is seen with a number of wars and global destructions ensuing with the nation of Israel at the center of the controversies.
Armageddon is simply the final conflict that is used to defeat the Antichrist and the nations that support him as they gather to defeat the tiny nation of Israel for good.. At that time, Jesus is left as the sole world leader when they learn that Israel is a stone that cannot be moved.... "a stumbling block for all nations".
After the conflict, about a 1/3 of the earth's current population will still be left over from the wars of the Anti-Christ. Of these, those that were kind to the nation of Israel, "Christ's Brothers", will be allowed entry into Christ's Millennium reign. Those nations and peoples caught up in the irrational hatred of Israel and who worked for its demise, are not allowed to enter.
Note: Both groups are surprised that their fate is decided on how they treated Israel.
Remember, God still has a plan for Israel after the Church age is consummated. Romans 11:
I say then, has God cast away His people? Certainly not! For I also am an Israelite, of the seed of Abraham, of the tribe of Benjamin. 2 God has not cast away His people whom He foreknew.......
For I do not desire, brethren, that you should be ignorant of this mystery, lest you should be wise in your own opinion, that blindness in part has happened to Israel until the fullness of the Gentiles has come in. 26 And so all Israel will be saved,