My comment that you quoted was about eternity...not the 1000 yr reign of Christ. I don't know what will happen after there is a new heaven and new earth. For all I know God may create new heavens and new earths again and again for His own pleasure. I feel certain that He didn't just create us and then sit down and twiddle His thumbs. I think He is still creating right now. Jesus said He was going to make a place for us, so we could be with Him. He's creating something. I have always believed that it was the beautiful city of God, the New Jerusalem, that comes down out of heaven that only His people could enter and everyone else could not.
I think you are worried that I'm saying that when Jesus returns that unbelievers that are still alive at his return (at the beginning of the 1000 yrs) could have a chance to be saved. Ok, you may have me there. It's true, I was thinking that if they are still alive and have not died, that they may still have a chance to believe in Christ before they die natural deaths during the 1000 years. I'm not including the non-resurrected people in this. Only the ones that are still alive after the tribulation. You say the cut off point for believing is when Jesus returns and the end comes...and I say the cut off point is when satan is released to deceived the nations again and the end comes. (which is after the 1000 yrs is over)
Now whether the 1000 yrs are a time for God to fulfill His promises to Israel...I don't know. Some say it is.