After the Millennial reign of Christ, and the banishment of Satan to the Lake of Fire, I assume eternity also begins for all believers who are on earth. Will it be possible for anyone who resides on the New Earth to lose their salvation? Will it always be a faith plus works combination for them to maintain their salvation, even in eternity? Or will their salvation ever be secure?
The Bible ends at the point where eternity begins, so it doesn’t reveal anything about our eternal state. However, from my study of 1 Cor. 15:20-28, I believe the only ones who will inhabit eternity will be believers in their perfected state (like we will be after the rapture). That means everyone will be immortal, with no more sin nature, and with God’s will the only will in Creation. Therefore, protecting or maintaining our salvation will no longer be an issue.