This was a part of Jesus’ answer to the disciples questions concerning end times. The Greek word translated “nations” is ethnos (ἔθνος). It might also be translated every race/culture/tongue. According to Wycliffe Bible Translators, there are still 350 million people in the world who do not have a Scripture translation in their heart language. And according to the www.joshuaproject.net 43% of the world’s people groups are still unreached. Most of these are in the 10/40 window. There are still “ethnos” who have not heard the gospel. God is still asking, “Whom shall I send and who will go for us?” (Isa.6:8).