I read it again slowly, The thesis of the OP, IMHO, is that those born during the millennium do not have a chance. They will all rebel at the end. I do not know but, Thank God, God knows.
The OP might even say if you survive the tribulation you end up with 1000 years of bliss then the Lake of Fire awaits? I do not know but, Thank God, God knows.
But people born during that time will still have a sin nature and will have to be covered by the blood of Jesus, just like people now, to be forgiven of their sin and have eternal life.
Not everyone will turn against Christ during that time, but a lot will.