There are many Scriptures that say we are to be in Christ, and many that say He is in us as believers ....but NONE support the idea that we are to become Christ. We are to be like Him but we never will be Him.
John 14:15-18
[15]If ye love me, keep my commandments.
[16]And I will pray the Father, and he shall give you another Comforter, that he may abide with you for ever;
[17]Even the Spirit of truth; whom the world cannot receive, because it seeth him not, neither knoweth him: but ye know him; for he dwelleth with you, and shall be in you.
[18]I will not leave you comfortless: I will come to you.
John 15:4-9
[4]Abide in me, and I in you. As the branch cannot bear fruit of itself, except it abide in the vine; no more can ye, except ye abide in me.
[5]I am the vine, ye are the branches: He that abideth in me, and I in him, the same bringeth forth much fruit: for without me ye can do nothing.
[6]If a man abide not in me, he is cast forth as a branch, and is withered; and men gather them, and cast them into the fire, and they are burned.
[7]If ye abide in me, and my words abide in you, ye shall ask what ye will, and it shall be done unto you.
[8]Herein is my Father glorified, that ye bear much fruit; so shall ye be my disciples.
[9]As the Father hath loved me, so have I loved you: continue ye in my love.
Galatians 2:20
[20]I am crucified with Christ: nevertheless I live; yet not I, but Christ liveth in me: and the life which I now live in the flesh I live by the faith of the Son of God, who loved me, and gave himself for me.
Colossians 1:27
[27]To whom God would make known what is the riches of the glory of this mystery among the Gentiles; which is Christ in you, the hope of glory:
Romans 8:9-10
[9]But ye are not in the flesh, but in the Spirit, if so be that the Spirit of God dwell in you. Now if any man have not the Spirit of Christ, he is none of his.
[10]And if Christ be in you, the body is dead because of sin; but the Spirit is life because of righteousness.
1 John 3:1-2
[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.
[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.