The answer to your question is found in the part of this portion of scripture which I highlighted in red.
Rom 8:15
For ye have not received the spirit of bondage again to fear; but
ye have received the Spirit of adoption, whereby we cry, Abba, Father.
Rom 8:16
The Spirit itself beareth witness with our spirit, that we are the children of God:
Rom 8:17
And if children, then heirs; heirs of God, and joint-heirs with Christ; if so be that we suffer with
him, that we may be also glorified together.
Rom 8:18
For I reckon that the sufferings of this present time
are not worthy
to be compared with the glory which shall be revealed in us.
Rom 8:19
For the earnest expectation of the creature waiteth for the manifestation of the sons of God.
Rom 8:20
For the creature was made subject to vanity, not willingly, but by reason of him who hath subjected
the same in hope,
Rom 8:21
Because the creature itself also shall be delivered from the bondage of corruption into the glorious liberty of the children of God.
Rom 8:22
For we know that the whole creation groaneth and travaileth in pain together until now.
Rom 8:23
And not only
they,
but ourselves also, which have the firstfruits of the Spirit, even we ourselves groan within ourselves, waiting for the adoption, to wit, the redemption of our body.
Rom 8:24
For we are saved by hope: but hope that is seen is not hope: for what a man seeth, why doth he yet hope for?
Rom 8:25
But if we hope for that we see not,
then do we with patience wait for
it.
As John said in his first epistle:
1Jo 3:1
Behold, what manner of love the Father hath bestowed upon us, that we should be called the sons of God: therefore the world knoweth us not, because it knew him not.
1Jo 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.
Christians are now the sons of God, BUT it does 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.
As I recently explained, Christians have currently received
the Spirit of adoption, but their adoptions are not yet complete, nor will they be, until Christ's second coming when the awaited and hoped for
adoption, or the redemption of their bodies, is complete. This is basically the same thing that John said. In other words, although we are presently accounted as being sons (and daughters) of God, we will not see him as he is, or we will not receive glorified bodies like his, or our adoptions will not be complete, until he appears a second time.
Your confusion seems to be directly linked to your misunderstanding of the word
adoption when used in scripture. In other words, it does not carry the same meaning that it carries in our day and age. Instead, it literally means "to place as an adult son." Again, it pertained in Paul's day to a coming-of-age ceremony, and part of that ceremony was the donning of a new outer garment. Christians will symbolically get new outer garments when mortality is swallowed up of immortality or when they receive their glorified bodies at Christ's second coming. This is the only thing that Christians, according to scripture, have been
predestinated to. All of the nonsense that Calvin and his beguiled followers have attached to the word
predestinated are non-biblical. This is the truth; like it or not.