If you are not a son now, you are not saved. It is that simple.No verse says we are placed as sons when we are born anew. Not one.
But Romans 8:23 says we receive the promised resurrection when we are placed as sons. So, rather than adoption, son-placing refers to our promised resurrection.
As to your assertion, it is false.
Galatians 4:6 And because ye are sons, God hath sent forth the Spirit of his Son into your hearts, crying, Abba, Father.
7 Wherefore thou art no more a servant, but a son; and if a son, then an heir of God through Christ.
These verses speak in the context of adoption. Because we are NOW adopted sons, and not servants of bondage we are also heirs. We have an inheritance. And as an extra added bonus, what other privilege do we have?
Galatians 4:6 And because ye are sons, God hath sent forth the Spirit of his Son into your hearts, crying, Abba, Father.
--It is the adopted sons of God that can truly call the Father "Abba." This is something you fail to understand. We don't have to wait for the resurrection to have that intimate relationship with him. We can have it now, through our adopted status as "mature" sons.
Galatians 4:30 Nevertheless what saith the scripture? Cast out the bondwoman and her son: for the son of the bondwoman shall not be heir with the son of the freewoman.
--If you are not a son NOW, at the time of the resurrection you will not receive a glorified body; you will be cast out, rejected.
Hebrews 12:6 For whom the Lord loveth he chasteneth, and scourgeth every son whom he receiveth.
7 If ye endure chastening, God dealeth with you as with sons; for what son is he whom the father chasteneth not?
8 But if ye be without chastisement, whereof all are partakers, then are ye bastards, and not sons.
--Four times in three verses is the word "son" used. Each time the word "uios" is used. The word" tekna" is the more general word used for child, children, etc. This word, uios, son, is the same word used in adoption or "son-placement."
Romans 8:14 For as many as are led by the Spirit of God, they are the sons of God.
--You are not led by the Spirit of God?? Do you have to wait for the resurrection? The word "uios" is used here.
Ephesians 3:5 Which in other ages was not made known unto the sons of men, as it is now revealed unto his holy apostles and prophets by the Spirit;
Philippians 2:15 That ye may be blameless and harmless, the sons of God, without rebuke, in the midst of a crooked and perverse nation, among whom ye shine as lights in the world;
1 John 3:2 Beloved, now are we the sons of God, and it doth not yet appear what we shall be: but we know that, when he shall appear, we shall be like him; for we shall see him as he is.
Have I made my case yet?