Thank you for the question on hearing the Gospel of Salvation, “Does everyone worldwide have to hear the gospel of Christ before his return?”
In Acts 1:8, Jesus declared to his disciples that they are to be witnesses in Jerusalem, Judea, Samaria, and to ends of the earth as well as make disciples of all nations or people group (Matt. 28:18–20).
The Gospel in our generation has nearly reached every people group in our world, even to the most remotest parts of our earth. The Scriptures are being translated into many language groups electronically.
Thus the general principle is that the Gospel is to be preached to the most remote places on earth, not that every person has too hear it. It was the Apostle Paul’s desire to preach the Gospel to unreached people. He had a debt to pay to the non-Jews for he wanted them to hear of the grace of God.
For more perspectives:
https://www.quora.com/Does-everyone-worldwide-have-to-hear-the-gospel-of-Christ-before-his-return