Aineo, there are many who will fall away. Not from being born again, but from the faith they profess with words but not with their hearts nor their lives. As John writes: "they went out from us, but they did not really belong to us."
Those who are in truth born again are and will always be the children of God by adoption through Jesus Christ.
Apostacy is what we, as men, see as falling away from apparent salvation. But we cannot judge men's hearts, and the fact that there are apostates shows clearly that God not only knows their hearts, but allows them to finally show their true selves to the rest of us.
But as for me, I know that nothing, not even my own self, can separate me from the love of God in Christ Jesus. I am born again in Him, and although I may occasionally have spiritual immature temper tantrums, I am His, and His forever.