Galatians 3:28-29 states that there is neither Jew nor Gentile, neither slave nor free, nor male and female, for you are all one in Christ Jesus. If you belong to Christ, then you are Abraham’s seed, and heirs according to the promise.
Yes, God’s plan all along was to do this - to break down the barriers between Jew and Gentile, slave and free, male and female. Christians are the wild olive branch grafted in.